Biology subjects

Nir, I.

Publications and source records attributed to Nir, I..

7 recordsLinked to original sources

bioRxiv2026

β-Carbonic anhydrase SlβCA4 is required for normal growth, carbon assimilation and stomatal plasticity in tomato

{beta}-Carbonic anhydrases ({beta}CAs) catalyze the reversible interconversion of CO2 and bicarbonate and contribute to plant carbon metabolism and environmental responses. However, the physiological functions of individual {beta}CA isoforms in crops remain poorly understood. Here, we investigated two chloroplast-localized {beta}CAs, Sl{beta}CA1 and Sl{beta}CA4, in tomato (Solanum lycopersicum). We combined subcellular localization, CRISPR/Cas9 mutagenesis, grafting, leaf gas-exchange measurements, and controlled environmental treatments to examine their roles in growth, photosynthesis, and stomatal developmental plasticity. Both proteins localized to chloroplasts but their disruption resulted in markedly different phenotypes. While Sl{beta}CA1 mutants showed largely normal growth and photosynthesis, Sl{beta}CA4 mutants exhibited severe root and shoot growth defects. Grafting mutant shoots onto wild-type rootstocks partially restored vegetative growth, indicating that impaired root function contributes to the growth defects. Sl{beta}CA4 mutants also showed reduced CO2 assimilation and stomatal conductance, while electron transport remained largely unaffected. Elevated CO2 partially improved leaflet growth but did not restore plant height or root elongation. Furthermore, unlike wild-type plants, Sl{beta}CA4 mutants failed to increase stomatal index in response to elevated temperature. These findings reveal distinct physiological roles for chloroplast-localized {beta}CAs in tomato and identify Sl{beta}CA4 as an important contributor to plant growth, photosynthesis, and temperature-dependent stomatal developmental plasticity.

plant biology↗

bioRxiv2026

Adventitious roots facilitate surface water uptake but only partially sustain transpiration under waterlogging in tomato (Solanum lycopersicum)

waterlogging constrains terrestrial plants by limiting oxygen diffusion in the rhizosphere and altering root-zone physical and chemical properties. However, the extent to which whole-plant responses to waterlogging can be reproduced by oxygen deficiency alone remains unresolved. In tomato (Solanum lycopersicum), waterlogging is commonly associated with adventitious-root formation, yet the functional contribution of these roots to whole-plant water relations has rarely been quantified. Here, we experimentally separated root-zone hypoxia from waterlogging and quantified the contribution of surface-associated adventitious roots to whole-plant transpiration. Using high-resolution gravimetric lysimeters, we monitored transpiration dynamics under two conditions: (i) N2-driven displacement of root-zone O2 under near-field-capacity conditions and (ii) root-zone waterlogging. These measurements were complemented by analyses of soil redox potential and pH, mineral composition, stem anatomy, and genotypic variation among M82, IL11-4, and IL8-1. N2-driven oxygen depletion rapidly reduced rhizosphere O2 concentration and induced a moderate decline in redox potential, accompanied by changes in rhizosphere chemistry and mineral relations. Whole-plant transpiration, however, declined only progressively over several days. Under waterlogging, transpiration declined rapidly in all genotypes, with strong genotype dependence. A transient partial recovery coincided with the appearance of adventitious roots at the soil surface and was followed by renewed decline after drainage. Quantitative analysis indicated that adventitious roots contributed only a limited fraction of daily water uptake, approximately 15% to 20%, which was insufficient to restore pre-waterlogging transpiration or growth. Together, these results show that waterlogging responses were not reproduced by rapid oxygen deprivation alone and that adventitious roots provide limited hydraulic compensation.

plant biology↗

bioRxiv2026

Genetic encoding of climate-responsive stomatal developmental plasticity in tomato

Flexible developmental programs enable plants to customize their organ size and cellular composition. In leaves of eudicots, the stomatal lineage produces two essential cell types, stomata and pavement cells, and plants can adjust the total numbers and ratios of these cell types in response to external cues. Central to this flexibility is the stomatal lineage-initiating transcription factor, SPEECHLESS (SPCH). Here we explore the mechanisms underlying SPCHs involvement in environmental response. Using multiplexed CRISPR/Cas9 editing of SlSPCH cis-regulatory sequences in tomato, we identified variants with altered stomatal development responses to drought, light and temperature cues. By creating and live-cell tracking translational reporters of SlSPCH and its paralogues SlMUTE and SlFAMA, we revealed the corresponding cellular events that lead to the environmental change-driven responses in stomatal production and leaf form. Plants bearing the novel reporters and SlSPCH variants are powerful resources for fundamental and applied studies of tomato resilience in response to climate change.

plant biology↗

bioRxiv2023

Targeting editing of tomato SPEECHLESS cis-regulatory regions generates plants with altered stomatal density in response to changing climate conditions

Flexible developmental programs enable plants to customize their organ size and cellular composition. In leaves of eudicots, the stomatal lineage produces two essential cell types, stomata and pavement cells, but the total numbers and ratio of these cell types can vary. Central to this flexibility is the stomatal lineage initiating transcription factor, SPEECHLESS (SPCH). Here we show, by multiplex CRISPR/Cas9 editing of SlSPCH cis-regulatory sequences in tomato, that we can identify variants with altered stomatal development responses to light and temperature cues. Analysis of tomato leaf development across different conditions, aided by newly-created tools for live-cell imaging and translational reporters of SlSPCH and its paralogues SlMUTE and SlFAMA, revealed the series of cellular events that lead to the environmental change-driven responses in leaf form. Plants bearing the novel SlSPCH variants generated in this study are powerful resources for fundamental and applied studies of tomato resilience in response to climate change. Significance statementPlants can change their shape, size and cellular composition in response to environmental cues. Here, by precise gene editing of a core stomatal development regulator gene in tomato, we generate new alleles with enhanced or dampened responses to light and temperature cues. Combined with live imaging of development, we show the genetic and cellular pathways that contribute to customization of the leaf epidermis, and how this could lead to better climate-adapted varieties.

plant biology↗

bioRxiv2023

Light perception by the root is essential for gibberellin-induced primary-root elongation in tomato

O_LIThe promoting effect of gibberellin (GA) on primary-root elongation is well-documented in several plant species, yet its influence in others, including tomato (Solanum lycopersicum), remains unclear. C_LIO_LIThe role of GA in primary-root elongation has been studied in tomato using the GA-deficient mutants gib-1 and ga20-oxidase (ga20ox1) and various growth systems, including Dark (D)-root and D-shoot plates. C_LIO_LIGA application to these mutants following germination on vermiculite, promoted primary-root elongation. However, when the roots grew deeper into the dark environment the hormone had no effect. RNA-seq analysis of dark-grown roots, treated with GA, revealed typical transcriptional responses, but the output for cell expansion remained unaffected. When dark-grown roots were illuminated deep in the ground, the hormone promoted their elongation. The results suggest that activation of Phytochrome B (PhyB) in the root, by red light, is essential for GA-induced elongation. C_LIO_LIWe propose that GA promotes tomato root elongation after germination, when roots are exposed to low light underground and this contributes to rapid seedling establishment. As roots penetrate deeper into the soil, insensitivity to GA due to the lack of light may be important for sustained root growth under fluctuating water availability, given that water deficiency suppresses GA accumulation. C_LI

plant biology↗

bioRxiv2021

On the edge: Evolution of polarity protein BASL and the capacity for stomatal lineage asymmetric divisions

Asymmetric and oriented stem cell divisions enable the continued production of patterned tissues. The molecules that guide these divisions include several "polarity proteins" that are localized to discrete plasma membrane domains, are differentially inherited during asymmetric divisions, and whose scaffolding activities can guide division plane orientation and subsequent cell fates. In the stomatal lineages on the surfaces of plant leaves, asymmetric and oriented divisions create distinct cell types in physiologically optimized patterns. The polarity protein BASL is a major regulator of stomatal lineage division and cell fate asymmetries in Arabidopsis, but its role in the stomatal lineages of other plants is unclear. Here, using phylogenetic and functional assays, we demonstrate that BASL is a eudicot-specific polarity protein. Among dicots, divergence in BASLs roles may reflect some intrinsic protein differences, but more likely reflects previously unappreciated differences in how asymmetric cell divisions are employed for pattern formation in different species. This multi-species analysis therefore provides insight into the evolution of a unique polarity regulator and into the developmental choices available to cells as they build and pattern tissues. HIGHLIGHTSO_LIBASL is a eudicot-specific regulator of stomatal lineage asymmetric cell divisions C_LIO_LIBASL protein evolution includes stepwise addition of polarity domains to an ancestral MAPK-binding chassis C_LIO_LICellular quiescence and BASL-guided polarity generate proper stomatal spacing in tomato C_LIO_LICell size and fate asymmetries are uncoupled in the tomato stomatal lineage C_LI

plant biology↗

bioRxiv2020

Mutations in the tomato gibberellin receptors suppresses xylem proliferation and reduces water loss under water-deficit conditions

Low gibberellin (GA) activity in tomato (Solanum lycopersicum) inhibits leaf expansion and reduces stomatal conductance. These lead to lower transpiration and improve water status under transient drought conditions. Tomato has three GIBBERELLIN-INSENSITIVE DWARF1 (GID1) GA receptors with overlapping activities and high redundancy. We have tested whether mutation in a single GID1 reduces transpiration without affecting growth and productivity. CRISPR-Cas9 gid1 mutants were able to maintain higher leaf water content under water-deficit conditions. Moreover, while gid1a exhibited normal growth, it showed reduced whole plant transpiration and better recovery from dehydration. Mutation in GID1a inhibited xylem vessels proliferation that led to lower hydraulic conductance. In stronger GA mutants, we also found reduced xylem vessel expansion. These results suggest that low GA activity affects transpiration by multiple mechanisms; it reduces leaf area, promotes stomatal closure and reduces xylem proliferation and expansion and as a result, xylem hydraulic conductance. We further examined if gid1a perform better than the control M82 in the field. Under these conditions, the high redundancy of GID1s was lost and gid1a plants were semi-dwarf, but their productivity was not affected. Although gid1a did not perform better under drought conditions in the field, it exhibited higher harvest index. HighlightThe loss of the tomato gibberellin receptors GID1s reduced xylem proliferation and xylem hydraulic conductance. These contribute to the effect of low gibberellin activity on water loss under water-deficit condition.

plant biology↗