Biology subjects

Saavedra, L. L.

Publications and source records attributed to Saavedra, L. L..

5 recordsLinked to original sources

bioRxiv2025

The interplay between autophagy and the carbon/nitrogen ratio as key modulator of the auxin-dependent chloronema-caulonema developmental transition in Physcomitrium patens.

Plants, as sessile living systems, have the capacity to respond to both internal and external signals by modulating their growth and developmental programs. Autophagy is a recycling process which is known to respond to these signals, yet its role as an integrative regulatory node coordinating environmental inputs and developmental outputs remains underexplored, particularly outside model angiosperms like Arabidopsis thaliana. Here, we investigate how the fluctuating supply of carbon and nitrogen modulates autophagy in relation to the auxin-driven chloronema-to-caulonema transition in the bryophyte Physcomitrium patens. We show that autophagy-deficient mutants display a loss of coordinated plasticity in response to the changing C/N supply ratio, exhibiting an initially enhanced yet ultimately unsustainable response to nitrogen deficiency alongside attenuated responses to external sucrose. These altered responses reflect a modified basal state in the mutants, evidenced by higher intrinsic caulonemal growth, sucrose accumulation, altered auxin homeostasis, and differential auxin-related gene expression. Consistent with this, exogenous auxin elicits a diminished developmental response but accelerates senescence in the mutants. Finally, we demonstrate how autophagic flux is dynamically modulated by the C/N supply ratio and show that it is activated when this ratio is most unbalanced. We propose that high autophagic activity is associated with chloroplast-rich chloronemal cells, whereas caulonemata-inducing conditions decrease autophagic flux. This implies a cell-type-specific modulation of autophagy, where it is negatively correlated with caulonemal development. Together, our findings identify autophagy as a key regulator within the system that modulates ordered and adaptive responses to both external nutrient availability and internal hormonal signaling. HIGHLIGHTSAutophagy coordinates carbon/nitrogen supply with developmental programs in P. patens. Autophagy negatively correlates with auxin-driven caulonemal development. Autophagy-deficient mutants lose coordinated plasticity. atg mutants exhibit a modified basal state with altered sugar and auxin profiles.

plant biology↗

bioRxiv2023

DIFFERENTIAL EFFECTS OF REACTIVE OXYGEN SPECIES ON AUTOPHAGY IN ARABIDOPSIS

Autophagy plays a key role in the responses to different stress condition in plants. Reactive oxygen species (ROS) are common modulators of stress responses, having both toxic and signaling functions. In this context, the relationship between ROS and autophagy regulation remains unclear, and in some aspects, contradictory. In this study, we employed pharmacological and genetic approaches to investigate the effects of different ROS on the cytoplastic redox state and autophagic flux in Arabidopsis thaliana. Ours results demonstrated that oxidative treatments with H2O2 and MV, which drastically increased the oxidized state of the cytoplasm, reduced the autophagic flux. Conversely, singlet oxygen, which did not have significant effects on the cytoplasmic redox state, increased the autophagic flux. Additionally, our findings indicated that after H2O2 and high light treatments and during the recovery period, the cytoplasm returned to its reduced state, while autophagy was markedly induced. In summary, our study unveils the differential effects of ROS on the autophagic flux, establishing a correlation with the redox state of the cytoplasm. Moreover, it emphasizes the dynamic nature of autophagy in response to oxidative stress and the subsequent recovery period. HIGHLIGHTSO_LIThis research shows the differential effects of reactive oxygen species on autophagic modulation, highlighting their impact on the cytoplasmic redox state. The relationship between ROS and autophagy regulation remains unclear, and in some aspects contradictory. Here, we present a comprehensive investigation characterizing the effects of different ROS, such as hydrogen peroxide and singlet oxygen, on the modulation of autophagy in Arabidopsis. In brief, our findings reveal differential impacts on cytoplasmic redox states and autophagic flux, providing insight into the dynamic nature of autophagy, especially in stress and post-stress conditions. C_LIO_LITo the best of our knowledge, our work is the first to evaluate autophagic flux both during and after oxidative stress in plants. Our results indicate that this differentiation is crucial when analyzing the effects of oxidative stress on autophagy. C_LI

cell biology↗

bioRxiv2022

Autophagy modulates apical growth and development in the moss Physcomitrium patens

Different to root hairs and pollen tubes, Physcomitrium patens apical growing protonemal cells have the singularity that they continue to undergo cell divisions as the plant develops, allowing to study autophagy in the context of a multicellular apical growing tissue coupled to development. Herein, we showed that the core autophagy machinery is present in the moss P. patens, and deeply characterized the growth and development of wild-type, atg5 and atg7 loss-of-function mutants under optimal and nutrient-deprived conditions. Our results showed that the growth of the different morphological and functional protonemata apical growing cells, chloronema and caulonema, is differentially modulated by this process. These differences depend on the protonema cell type and position along the protonemal filament, and growth condition. As a global plant response, the absence of autophagy triggers the spread of the colony through protonemata growth at the expense of a reduction in buds and gametophore development, and thus the adult gametophytic and reproductive phases. Altogether this study provides valuable information indicating that autophagy has roles during apical growth with differential responses within the cell types of the same tissue and contributes to life cycle progression and thus the development of the 2D and 3D tissues of P. patens. HIGHLIGHTAutophagy is differentially induced in protonemal cells, and contributes to apical growth, life cycle progression, and thus the development of the 2D and 3D tissues of P. patens.

plant biology↗

bioRxiv2020

Genome-wide identification, characterization and expression analysis of the Bcl-2 associated athanogene (BAG) gene family in Physcomitrium patens

The Bcl-2-associated athanogene (BAG) family is an evolutionarily conserved, multifunctional group of co-chaperones regulators that modulate a number of diverse processes. Plant BAG genes were identified to play an extensive role in processes of programmed cell death (PCD) ranging from growth and development to stress responses. In this study, we identified BAG genes from different photosynthetic organisms in order to gather evolutionary insights on these proteins followed by an in silico characterization of the BAG family in the bryophyte Physcomitrium patens. Ten putative PpBAGs harbouring a characteristic BAG domain were grouped into two subfamilies based on the presence of additional conserved domains and phylogenetic distances. Group I consisted of PpBAG4 and PpBAG5, containing an additional ubiquitin-like domain, and PpBAG10 with only the BAG domain. Group II consisted of PpBAG1-3 and PpBAG6-9, containing a calmodulin-binding IQ motif, a novel feature associated with plant BAG proteins. Interestingly, PpBAG9 exhibits an EF-Hand domain, not reported to date in this class of proteins. Caspase cleavage sites in PpBAG1, PpBAG3, PpBAG4-5 and PpBAG9 were predicted. In silico analysis of BAG genes revealed the presence of stress responsive elements, and a stress-regulated expression pattern which appears to be dependent on specifically organized promoter regulatory elements. According to our analyses, the present data suggest that some members of P. patens BAG gene family may play a role in heat responses, autophagy and pathogen immunity. Further studies are required to unveil the role of specific members of this gene family in PCD and stress responses in P. patens. Key messageGenome-wide identification and phylogenetic relationships combined with in silico gene-expression profiling and protein-interaction analysis of PpBAGs in Physcomitrium patens, highlight the importance of a particular set in stress tolerance.

plant biology↗

bioRxiv2019

Evolutionary insights into PtdIns3P signaling through FYVE and PHOX effector proteins from the moss Physcomitrella patens.

Phosphatidylinositol 3-phosphate (PtdIns3P) is one of the five different phosphoinositides (PPIs) species in plant cells, which regulate several aspects of plant growth and development, as well as responses to biotic and abiotic stresses. The mechanistic insights underlying PtdIns3P mode of action, specifically through PtdIns3P-binding effectors such as FYVE and PHOX proteins have been partially explored in plants with main focus on Arabidopsis thaliana. Additionally, they have been underexplored in other plant organisms such as bryophytes, the earliest diverging group of terrestrial flora.\n\nIn this study, we searched for genes coding for FYVE and PHOX domains containing sequences from different photosynthetic organisms in order to gather evolutionary insights on these PPI binding domains, followed by an in silico characterization of the FYVE and PHOX gene family in the moss Physcomitrella patens. Phylogenetic analysis showed that PpFYVE proteins can be grouped in 7 subclasses, with an additional subclass whose FYVE domain was lost during evolution to higher plants. On the other hand, PpPHOX proteins are classified into 5 subclasses. Expression analyses based on RNAseq data together with the analysis of cis-acting regulatory elements and transcription factor binding sites in promoter regions suggest the importance of these proteins in regulating stress responses but mainly developmental processes in P. patens. The results provide valuable information and robust candidate genes for future functional analysis aiming to further explore the role of this signaling pathway mainly during growth and development of tip growing cells and during the transition from 2D to 3D growth, which could provide ancestral regulatory players undertaken during plant evolution.

plant biology↗