Biology subjects

Ramon, U.

Publications and source records attributed to Ramon, U..

3 recordsLinked to original sources

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↗

bioRxiv2020

Underground gibberellin activity: differential gibberellin response in tomato shoots and roots

Gibberellins (GAs) are growth-promoting hormones that regulate organ growth, mainly via cell elongation. Contradicting reports leave an open question of whether GA is as important for root elongation as it is for stem elongation. Here we have addressed this question focusing on tomato (Solanum lycopersicum) primary-root elongation. We used a combination of physiological, molecular and genetic approaches to tackle this question. Tomato has three GA receptors; GID1a, GID1b1 and GID1b2. The loss of all three receptors, strongly suppressed stem elongation and leaf expansion, but had a relatively minor effect on primary root elongation. The effect of GA on cell elongation and gene-expression was much weaker in roots, than in shoots, reaching saturation at lower hormone concentrations. Our results imply that this differential response to GA in shoots and roots is caused by the lower expression of the dominant GA receptor GID1a in roots. We show that the differential activity of GA between shoots and roots affects root-to-shoot ratio, and speculate that this evolved as an adaptive mechanism to changing environments.

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↗