Biology subjects

Rodriguez-Concepcion, M.

Publications and source records attributed to Rodriguez-Concepcion, M..

18 recordsLinked to original sources

bioRxiv2026

A photostable version of HY5 confers tolerance to proximity shade and improved defense responses in tomato

Light is essential for plant growth and development. Sustainably feeding a constantly-growing human population will likely involve adapting crop plants to intercropping and high planting density by rational manipulation of light signaling. Here, we edited the tomato (Solanum lycopersicum) genome to generate lines with a light-stable version of ELONGATED HYPOCOTYL 5 (HY5), a master transcription factor involved in the integration of light and hormone signaling. Removing the tomato HY5 N-terminal domain required for interaction with CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1) prevented light-dependent protein degradation and resulted in a gain-of-function phenotype of short seedlings. Elongation growth was also compromised under proximity shade conditions either simulated by enriching white light (W) with far-red light (W+FR) or achieved by growing plants at a higher density. Transcriptomic analysis of gene expression changes after exposure to W+FR for 24h revealed a reduced number of shade-responsive genes in edited lines compared to unedited, wild-type controls, many of which are related to growth and hormone (notably auxin) biosynthesis and signaling. The reduced elongation observed in edited lines correlated with enhanced resistance to infection by viral, bacterial and fungal pathogens, both under low and high density conditions. These results indicate that our editing approach allows the generation of gain-of-function tomato plants in which HY5 is camouflaged to avoid COP1 recognition and eventual degradation. Our findings therefore provide a biotechnological tool to create more compact and pathogen-resistant plants amenable to high planting densities.

plant biology↗

bioRxiv2025

Chemical modulation of chloroplast de- and re-differentiation reveals a role for the SAL1-PAP retrograde pathway in facilitating plastid transitions

Plastids are dynamic organelles that remodel their composition, ultrastructure, and function according to developmental and environmental demands. The synthetic molecule X57 induces the conversion of leaf chloroplasts into tocopherol-rich plastids lacking thylakoids and containing proliferating plastoglobules. Removal of X57 triggers chloroplast re-differentiation, enabling precise spatial-temporal dissection of these transitions. X57 directly binds and inhibits the phosphatase SAL1, causing accumulation of its substrate 3'-phosphoadenosine 5'-phosphate (PAP), a retrograde signal that modulates nuclear gene expression. SAL1 inhibition and subsequent PAP accumulation activate a cascade that depletes cytokinins and down-regulates GOLDEN2-LIKE1 (GLK1) and other transcription factors involved in chloroplast biogenesis. SAL1-defective mutants fail to undergo this signaling pathway. The SAL1-PAP-mediated weakening of chloroplast identity preconditions plastids for their eventual conversion into storage-type organelles upon X57-promoted accumulation of tocopherols. After X57 withdrawal, photosynthetic gene expression and chloroplast functions are restored. This framework identifies key molecular mechanisms underlying chloroplast plasticity, a central process in biology.

plant biology↗

bioRxiv2025

A melon (Cucumis melo) homologue of REPRESSOR OF PHOTOSYNTHETIC GENES prevents chloroplast differentiation in the fruit flesh

Fruit flesh color in melon can be orange, green or white, depending on the accumulation of the orange carotenoid {beta}-carotene or / and green chlorophylls. The dominant allele of Green flesh (Gf) causes orange melons, but in the absence of this allele the flesh of ripe melon can be white or green depending on the White flesh (Wf) locus, being white dominant over green. The identity of Wf has remained unclear despite several candidates have been proposed. Here we identified Wf by fine mapping of a segregating population derived from the white-fleshed variety Piel de Sapo (PS, gf gf / Wf Wf) and the orange-fleshed Vedrantais (VED, Gf Gf / wf wf). Wf corresponds to the gene MELO3C003098, herein referred to as CmRPGE1 as it encodes a fruit-specific homologue of REPRESSOR OF PHOTOSYNTHETIC GENES (RPGE) microproteins. Similar to RPGE homologues from other plants, overexpression of the PS allele (CmRPGE1PS) caused a pale green leaf phenotype in Nicotiana benthamiana and Arabidopsis thaliana. By contrast, a 10-nucleotide deletion in the VED allele (CmRPGE1VED) resulted in a loss of RPGE function. The active CmRPGE1PS microprotein interacts with a fruit-localized melon homologue of ARABIDOPSIS PSEUDO-RESPONSE REGULATOR2 (APRR2), a GARP family transcription factor. Binding of CmRPGE1PS retains the melon APRR2 homologue in the cytosol, hence preventing the regulation of target genes involved in chloroplast biogenesis. In green fruit cultivars, the non-functional CmRPGE1VED allele allows APRR2 to perform its function, leading to chloroplast development and consequently a green flesh phenotype. SIGNIFICANT STATEMENTFruit color is a critical quality trait that directly influences consumer preference and market value in melon. In this study, we demonstrate that the White flesh (Wf) gene, a major determinant of melon fruit flesh color, encodes a fruit-specific homologue of REPRESSOR OF PHOTOSYNTHETIC GENES (RPGE) microproteins. The encoded microprotein, CmRPGE1, interacts with melon homologues of ARABIDOPSIS PSEUDO-RESPONSE REGULATOR2 (APRR2), a GARP family transcription factor. In white flesh melons, the CmAPRR2.2 paralog is sequestered in the cytoplasm upon interaction with CmRPGE1, thereby preventing the expression of target genes involved in chlorophyll accumulation. Conversely, the truncated version of CmRPGE1 present in green-fleshed melons fails to interact with CmAPRR2.2 and to prevent its nuclear localization and function, allowing chloroplasts differentiation.

plant biology↗

bioRxiv2025

Loss of tomato geranylgeranyl diphosphate synthase 2 increases monoterpenoid levels and enhances immune responses to bacterial infection

Many plastidial isoprenoids, including diterpenes and photosynthesis-related isoprenoids such as carotenoids and chlorophylls, derive from C20 geranylgeranyl diphosphate (GGPP), produced by GGPP synthase (GGPPS) enzymes. Heterodimers of GGPPS and non-catalytic type I small subunit (SSU-I) proteins produce C10 geranyl diphosphate (GPP), the precursor of monoterpenes. Three plastidial GGPPS isoforms, referred to as SlG1-3, are present in tomato (Solanum lycopersicum). Here we explored their contribution to the production of volatile organic compounds (VOCs) of isoprenoid origin under normal conditions and in response to infection with Pseudomonas syringae pathovar tomato (Pst). Edited lines lacking SlG2 showed a distinctive VOC profile compared to unedited (WT) plants and mutants impaired in SlG1 or SlG3. In particular, only slg2 mutants showed constitutively increased levels of GPP-derived hydroxylated monoterpenes (HMTPs). Upon Pst infection, slg2 plants accumulated higher levels of salicylic acid (SA) and exhibited increase resistance compared to WT controls, resulting in reduced levels of VOCs associated to cell death. Our findings suggest that SlG2 regulates GPP synthesis, potentially by specifically competing with other GGPPS isoforms for heterodimerization with SSU-I. Increased GPP production in slg2 plants could lead to higher HMTPs levels, which may result in elevated SA content, and subsequently enhanced protection against bacterial infection.

plant biology↗

bioRxiv2025

A tomato line hyposensitive to simulated proximity shade shows altered auxin-related 1 gene expression and improved fruit yield under high-density field conditions

Plants detect the presence of nearby vegetation as a reduction in the ratio of red to far-red light (low R/FR). This proximity shade signal can be simulated in the lab by supplementing white light (W) with FR (W+FR). While shade avoidance strategies are considered undesirable in agricultural crops, FR supplementation enhances plant growth and fruit quality in tomato (Solanum lycopersicum). Here we compared the response of different tomato genotypes to W+FR in the lab and identified one S. pennellii introgression line (IL2-2) with a shade-tolerant phenotype at the seedling stage. Compared to the shade-avoider parental genotype M82, IL2-2 plants showed reduced elongation upon W+FR exposure and a disrupted expression of auxin-related genes both under W and W+FR. At harvest, W+FR treatment improved M82 fruit quality by increasing {degrees}Brix, ascorbic acid and carotenoids, and these quality traits remained virtually unchanged in IL2-2. Under high density (HD) conditions, fruit quality traits were hardly impacted by planting density or genotype, but IL2-2 showed improved fruit yield. Our findings suggest that IL2-2 could serve as a valuable genotype for high-density or intercropping agrosystems.

plant biology↗

bioRxiv2025

Activation of alternative oxidase ensures carbon supply for ethylene and carotenoid biosynthesis during tomato fruit ripening

Tomato (Solanum lycopersicum) is a climacteric fruit displaying a peak of respiration at the onset of ripening accompanied by increased synthesis of ethylene and carotenoid pigments. Chromoplast and mitochondrial respiration participate at different stages of fruit ripening, but their in vivo regulation and function remains unclear. We determined the in vivo activities of the mitochondrial alternative oxidase (AOX) and cytochrome oxidase pathways and quantified the levels of respiratory- and ripening-related gene transcripts, primary metabolites and carotenoids in ripening tomato fruits with or without a functional chromorespiration. Furthermore, we carried out physiological, molecular and metabolic analyses of CRISPR-Cas9 mutants defective in AOX1a, the main AOX isoform up-regulated during tomato fruit ripening. We confirmed that PTOX-dependent chromorespiration is only relevant at late stages of ripening and found that in vivo AOX activity significantly increased at the breaker stage, becoming the main contributor to climacteric respiration when ripening is unleashed. This activation did not correlate with gene expression but was likely due to increased levels of AOX activators such as pyruvate (a metabolic precursor of carotenoids), 2-oxoglutarate and succinate. A strong alteration of ripening-related metabolites was observed in aox1a mutant fruits, highlighting a key role of the AOX pathway at the onset of ripening. Our data suggest that increased supply of TCA cycle intermediates at climacteric stage allosterically enhance AOX activity, thus allowing the reoxidation of NAD(P)H to ensure carbon supply for triggering ethylene and carotenoid biosynthesis.

plant biology↗

bioRxiv2023

Boosting pro-vitamin A content and bioaccessibility in leaves by combining engineered biosynthesis and storage pathways with high-light treatments

The relevance of plants as food is expected to grow for a more sustainable diet. In this new context, improving the nutritional quality of plant-derived foods is a must. Biofortification of green leafy vegetables with pro-vitamin A carotenoids such as {beta}-carotene has remained challenging to date. Here we combined two strategies to achieve this goal. One of them (that we call strategy C) involves producing {beta}-carotene in extraplastidial locations of leaf cells to avoid the negative impacts on photosynthesis derived from changing the balance of carotenoids and chlorophylls in chloroplasts. The second approach (that we refer to as strategy P) involves the conversion of chloroplasts into non-photosynthetic, carotenoid-overaccumulating chromoplasts in some leaves, leaving other non-engineered leaves to sustain normal plant growth. Combination of these two strategies resulted in a 5- fold increase in the amount of {beta}-carotene in Nicotiana benthamiana leaves. Following several attempts to further improve {beta}-carotene leaf contents by metabolic engineering, hormone treatments and genetic screenings, it was found that promoting the proliferation of plastoglobules with high-light treatments not only improved {beta}-carotene accumulation but it also resulted in a much higher bioaccessibility. Combination of strategies C and P together with a high-light treatment increased the levels of accessible {beta}-carotene 30-fold compared to controls. We further demonstrate that stimulating plastoglobule proliferation with strategy P but also with high-light alone can also stimulate and hence improve {beta}-carotene contents and bioaccessibility in edible lettuce (Lactuca sativa) leaves, unveiling the power of non-GMO approaches for leaf biofortification.

plant biology↗

bioRxiv2023

Metabolic crosstalk between hydroxylated monoterpenes and salicylic acid in tomato defence response against Pseudomonas syringae pv tomato

Hydroxylated monoterpenes (HMTPs) are differentially emitted by tomato plants efficiently resisting a bacterial infection. We have studied the defensive role of these volatiles in the tomato response to bacteria, whose main entrance are stomata apertures. Treatments with some HMTPs resulted in stomatal closure and PR1 induction. Particularly, -terpineol induced stomatal closure in a salicylic (SA) and abscisic acid-independent manner, and conferred resistance to bacteria. Interestingly, transgenic tomato plants overexpressing or silencing the monoterpene synthase MTS1, which displayed alterations in the emission of HMTPs, exhibited changes in the stomatal aperture but not in plant resistance. Measures of both 2-C-methyl-D-erythritol-2,4-cyclopyrophosphate (MEcPP) and SA levels, revealed a competition for MEcPP by the methylerythritol phosphate (MEP) pathway and the SA biosynthesis activation, thus explaining the absence of phenotype in transgenic plants. These results were confirmed by chemical inhibition or activation of the MEP pathway. Besides, treatments with BTH, a SA functional analogue, conferred enhanced resistance in transgenic tomato plants overexpressing MTS1. Finally, plants overexpressing MTS1 induced PR1 and stomata closure in neighbouring plants. Our results confirm the role of HMTPs in both intra and inter-plant immune signalling, and reveal a metabolic crosstalk between the MEP and SA pathways in tomato plants. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=124 SRC="FIGDIR/small/539605v2_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@1048cddorg.highwire.dtl.DTLVardef@1bc1948org.highwire.dtl.DTLVardef@1ff0eaorg.highwire.dtl.DTLVardef@101c4fa_HPS_FORMAT_FIGEXP M_FIG Metabolic crosstalk between hydroxylated monoterpenes and salicylic acid in tomato defence response against Pseudomonas syringae pv tomato. Created with BioRender.com. C_FIG

plant biology↗

bioRxiv2022

Tomato geranylgeranyl diphosphate synthase isoform 1 specifically interacts with phytoene synthase isoform 3 to produce strigolactones in tomato roots.

O_LICarotenoids are photoprotectant pigments and precursors of the hormones abscisic acid (ABA) and strigolactones (SL). Carotenoids are produced in plastids from geranylgeranyl diphosphate (GGPP), which is diverted to the carotenoid pathway by phytoene synthase (PSY). In tomato (Solanum lycopersicum), 3 genes encode plastid-targeted GGPP synthases (SlG1 to 3) and 3 genes encode PSY isoforms (PSY1 to 3). C_LIO_LIHere we investigated the function of SlG1 by generating loss-of-function lines and combining their metabolic and physiological phenotypes with gene co-expression and co-immunoprecipitation analyses. C_LIO_LILeaves and fruits of slg1 lines showed a wild-type phenotype in terms of isoprenoid accumulation, photosynthesis and development. Consistently, SlG1 is co-expressed with PSY3 and other genes involved in the production of carotenoids and SL (but not ABA) only in roots. SlG1 was also found to physically interact with the root-specific PSY3 isoform (and not with PSY1 and PSY2). Root SL (but not ABA) levels were reduced in slg1 lines. C_LIO_LIOur results confirm a specific role of SlG1 in SL production in combination with PSY3. This role appears to be restricted to roots as slg1 plants do not exhibit the shoot phenotype displayed by other SL-deficient mutants. C_LI

plant biology↗

bioRxiv2022

Overlapping and specialized roles of tomato phytoene synthase isoforms PSY1 and PSY2 in carotenoid and ABA production

Carotenoids are plastidial isoprenoids required for photosynthesis and production of hormones such as abscisic acid (ABA) in all plants. In tomato (Solanum lycopersicum), carotenoids also provide color to flowers and ripe fruit. Phytoene synthase (PSY) catalyzes the first and main flux-controlling step of the carotenoid pathway. Three PSY isoforms are present in tomato, PSY1 to 3. Mutants have shown that PSY1 is the isoform providing carotenoids for fruit pigmentation but it is dispensable in photosynthetic tissues. No mutants are available for PSY2 or PSY3, but their expression profiles suggest a main role for PSY2 in leaves and PSY3 in roots. To further investigate isoform specialization with genetic tools, we created tomato edited lines defective in PSY1 and PSY2 in the MicroTom background. The albino phenotype of lines lacking both PSY1 and PSY2 confirmed that PSY3 does not contribute to carotenoid biosynthesis in shoot tissues. Our work further shows that carotenoid production in tomato shoots relies on both PSY1 and PSY2 but with different contributions in different tissues. PSY2 is the main isoform for carotenoid biosynthesis in leaf chloroplasts, but the supporting role of PSY1 is particularly important under high light. PSY2 also contributes to the production of carotenoids in flower petals and, to a lower extent, fruit chromoplasts. Most interestingly, our results demonstrate that fruit growth and ripening is controlled by ABA produced in the pericarp from PSY1-derived precursors whereas PSY2 provides precursors for ABA synthesis in seeds to control germination.

plant biology↗

bioRxiv2022

Arabidopsis FIBRILLIN6 regulates carotenoid biosynthesis by directly promoting phytoene synthase activity

Carotenoids are health-promoting plastidial isoprenoids with essential functions in plants as photoprotectants and photosynthetic pigments in chloroplasts. They also accumulate in specialized plastids named chromoplasts, providing color to non-photosynthetic tissues such as flower petals and ripe fruit. Carotenoid accumulation in chromoplast requires specialized structures and proteins such as fibrillins. Although fibrillins were first reported as structural components of carotenoid sequestering structures in chromoplasts, later work revealed roles in chloroplasts and other plastid types. However, the association of fibrillins with carotenoids in plastids other than chromoplasts has remained unexplored. Here we show that a member of the fibrillin family, FBN6, interacts with phytoene synthase (PSY, the first committed and rate-determining step of the carotenoid pathway) to promote its enzymatic activity. Transient overexpression of FBN6 in Nicotiana benthamiana leaves results in a higher production of phytoene, the product of PSY activity, whereas loss of FBN6 activity in Arabidopsis thaliana mutants dramatically reduces the production of carotenoids during seedling deetiolation and after exposure to high light. Our work hence demonstrates that fibrillins not only promote the accumulation of carotenoids but also their biosynthesis.

plant biology↗

bioRxiv2022

Novel insights on the contribution of plastoglobules and reactive oxygen species to chromoplast differentiation

Enriching plant tissues in phytonutrients can be done by stimulating their biosynthesis but also by providing appropriate sink structures for their sequestering and storage. Chromoplasts are plastids specialized in the production and accumulation of carotenoids that are naturally formed in non-photosynthetic tissues such as flower petals and ripe fruit. Chromoplasts can also be artificially differentiated from leaf chloroplasts by boosting the production of phytoene (the first committed intermediate of the carotenoid pathway) with the bacterial phytoene synthase crtB. Here we show that crtB-induced leaf chromoplasts develop plastoglobules harboring high levels of carotenoids (mainly phytoene and pro-vitamin A {beta}-carotene) but also other nutritionally-relevant isoprenoids such as tocopherols (vitamin E) and phylloquinone (vitamin K1). Further promoting plastoglobule proliferation by exposure to intense (high) light resulted in a higher accumulation of these health-related metabolites but also an acceleration of the chloroplast-to-chromoplast conversion. We further show that production of reactive oxygen species (ROS) stimulates chromoplastogenesis. Our data suggest that, similar to that already described for decreased photosynthesis and enhanced carotenoid biosynthesis, ROS production is not just a consequence but a promoter of the chromoplast differentiation process.

plant biology↗

bioRxiv2022

Chloroplast protein import determines plant proteostasis and retrograde signaling

Proteins containing polyglutamine (polyQ) repeats are prone to aggregation and can lead to distinct human pathologies. For instance, Huntingtons disease is caused by an abnormal expansion of the polyQ stretch (> Q35) of Huntingtin (HTT) protein. However, plants express hundreds of proteins containing polyQ regions, but no pathologies arising from these factors have been reported to date. Here, we ask how plants maintain the proteostasis of polyQ-containing proteins, which are intrinsically enriched in the plant proteomes. To this end, we overexpressed an aggregation-prone fragment of human HTT (Q69) in plant cells. In contrast to invertebrate and mammalian transgenic models, we find that Arabidopsis thaliana plants suppress Q69 aggregation. This elevated proteostasis ability is mediated through the import and degradation of Q69 in chloroplasts. Conversely, inhibition of chloroplast protein import either genetically or pharmacologically reduces the capacity of plant cells to prevent Q69 aggregation. We find that Q69 interacts with the chloroplast stromal processing peptidase (SPP). Notably, expression of synthetic Arabidopsis SPP is sufficient to suppress aggregation of polyQ-expanded HTT in human cells. Beyond ectopically expressed Q69-HTT, endogenous polyQ-containing proteins also aggregate in Arabidopsis upon inhibition of chloroplast import. Among them, the plastid casein kinase 2 (pCK2), which contains a polyQ region next to the chloroplast targeting sequence motif, can also be localized into the nucleus. Upon inhibition of chloroplast import, pCK2 accumulates at higher levels in the nucleus and forms diamond-shaped amyloid-like fibrils surrounding the chloroplasts. These results indicate that the differential conformation and redistribution of pCK2 to the nucleus depends on chloroplast import efficiency, providing a role of polyQ repeats in chloroplast to nucleus communication (i.e. retrograde signaling). Together, our findings establish chloroplast protein import and proteases as determinants of polyQ proteostasis, with important implications for plant biology that can also lead to therapeutic approaches for human diseases that involve protein aggregation.

plant biology↗

bioRxiv2022

Biosynthesis and apoplast accumulation of the apocarotenoid pigment azafrin in parasitizing roots of Escobedia grandiflora

O_LIThe herbaceous hemiparasite Escobedia grandiflora (Orobanchaceae) is used in traditional medicine in the Andean region. Their roots accumulate an orange pigment with a significant relevance as a cooking dye that exhibits antioxidant and cardioprotective properties. C_LIO_LIThe present work combined metabolic and cytological analyses with de novo transcriptome assembly, gene expression studies, and phylogenetic analyses to confirm the chemical identity of the pigment and investigate its biosynthesis and function in Escobedia roots. C_LIO_LIThe pigment was conclusively shown to be azafrin, an apocarotenoid likely derived from the cleavage of {beta}-carotene. Candidate genes for the production of azafrin in Escobedia roots are proposed based on RNA-seq supported by RT-qPCR and phylogeny reconstruction analyses. In particular, our data suggest that azafrin production relies a carotenoid cleavage dioxygenase (CCD) different from CCD7 and similar to CCD4 enzymes. We also show that azafrin is delivered to the root apoplast and that it accumulates in the area where the Escobedia haustorium contacts the hosts root, suggesting a role of azafrin in the parasitization process. C_LIO_LIAltogether, our work represents an unprecedented step forward in our understanding of the Escobedia parasitization system, but it also provides vital information towards the eventual domestication of this valuable medicinal plant. C_LI

plant biology↗

bioRxiv2021

Manipulation of carotenoid metabolism stimulates biomass and stress tolerance in tomato

Improving yield, nutritional value and tolerance to abiotic stress are major targets of current breeding and biotechnological approaches that aim at increasing crop production and ensuring food security. Metabolic engineering of carotenoids, the precursor of Vitamin-A and plant hormones that regulate plant growth and response to adverse growth conditions, has been mainly focusing on provitamin A biofortification or the production of high-value carotenoids. Here, we show that the introduction of a single gene of the carotenoid biosynthetic pathway in different tomato cultivars simultaneously improved photosynthetic capacity and tolerance to various abiotic stresses (e.g., high light, salt, and drought), caused an up to 77% fruit yield increase and enhanced fruits provitamin A content and shelf life. Our findings pave the way for developing a new generation of crops that combine high productivity and increased nutritional value with the capability to cope with climate change-related environmental challenges.

plant biology↗

bioRxiv2021

Carotenoid and tocopherol fortification of zucchini fruits using a viral RNA vector

Carotenoids and tocopherols are health-promoting metabolites in livestock and human diets. Some important crops have been genetically modified to increase their content. Although the usefulness of transgenic plants to alleviate nutritional deficiencies is obvious, their social acceptance has been controversial. Here, we demonstrate an alternative biotechnological strategy for carotenoid and tocopherol fortification of edible fruits in which no transgenic DNA is involved. A viral RNA vector derived from Zucchini yellow mosaic virus (ZYMV) was modified to express a bacterial phytoene synthase (crtB), and inoculated in zucchini (Cucurbita pepo L.) leaves nurturing pollinated flowers. After the viral vector moved to the developing fruit and expressed crtB, the rind and flesh of the fruits developed yellow-orange rather than green color. Metabolite analyses showed a substantial enrichment in health-promoting carotenoids, such as - and {beta}-carotene (pro-vitamin A), lutein and phytoene, in both rind and flesh. Considerably higher accumulation of - and {gamma}-tocopherol was also detected, particularly in fruit rind. Although this strategy is perhaps not free from controversy due to the use of genetically modified viral RNA, our work does demonstrate the possibility of metabolically fortifying edible fruits using an approach in which no transgenes are involved.

plant biology↗

bioRxiv2021

The intrinsic chaperone network of Arabidopsis stem cells confers protection against proteotoxic stress

The biological purpose of plant stem cells is to maintain themselves while providing new pools of differentiated cells that form organs and rejuvenate or replace damaged tissues1-3. Protein homeostasis, or proteostasis, is required for cell function and viability4-7. However, the link between proteostasis and plant stem cell identity remains unknown. In contrast to their differentiated counterparts, we find that root stem cells can prevent the accumulation of aggregated proteins even under proteotoxic stress conditions such as heat stress or proteasome inhibition. Notably, root stem cells exhibit enhanced expression of distinct chaperones that maintain proteome integrity. Particularly, intrinsic high levels of the TRiC/CCT chaperonin determine stem cell maintenance and their remarkable ability to suppress protein aggregation. Overexpression of CCT8, a key activator of TRiC/CCT assembly8, is sufficient to ameliorate protein aggregation in differentiated cells and confer resistance to proteotoxic stress in plants. Taken together, our results indicate that enhanced proteostasis mechanisms in stem cells could be an important requirement for plants to persist under extreme environmental conditions and reach extreme long ages. Thus, proteostasis of stem cells could provide insights to design and breed plants tolerant to environmental challenges caused by the climate change.

plant biology↗

bioRxiv2020

Light quality signals generated by vegetation shade facilitate acclimation to reduced light quantity in shade-avoider plants

O_LIWhen growing in search for light, plants can experience continuous or occasional shading by other plants. Plant proximity causes a decrease in the ratio of red to far red light (low R:FR) due to the preferential absorbance of red light and reflection of far red light by photosynthetic tissues of neighboring plants. This signal is often perceived before actual shading causes a reduction in photosynthetically active radiation (low PAR). C_LIO_LIHere we investigated elongation, photosynthesis and photoacclimation responses in several Brassicaceae species to explore the possible connections between low R:FR and low PAR. C_LIO_LIA negative correlation was found in shade-tolerant Cardamine hirsuta and shade-avoider Arabidopsis thaliana seedlings (e.g., shade-tolerance was associated with a good adaptation to low PAR but a poor or null response to low R:FR exposure). However, they could be genetically uncoupled. Most interestingly, exposure to low R:FR of shade-avoider plants improved their photoacclimation to low PAR by triggering changes in photosynthesis-related gene expression, pigment accumulation and chloroplast ultrastructure. C_LIO_LIThese results indicate that low R:FR signaling unleashes molecular, metabolic and developmental responses that allow shade-avoider plants (including most crops) to adjust their photosynthetic capacity in anticipation of eventual shading by nearby plants. C_LI

plant biology↗