Abstract
Low gibberellin (GA) activity in tomato (Solanum lycopersicum) inhibits leaf expansion and reduces stomatal conductance. This leads to lower transpiration and improved water status under transient drought conditions. Tomato has three GIBBERELLIN-INSENSITIVE DWARF1 (GID1) GA receptors with overlapping activities and high redundancy. We 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 vessel proliferation, which 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 performs 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 a higher harvest index.
Highlights
Drought has a major impact on plant development and food supply, and is responsible for major losses of crop productivity (Mittler and Blumwald, 2010).Plants have adopted various strategies to cope with water deficiency, including maintaining water status by stomatal closure, accumulation of osmolytes and stress related proteins and changes in growth and development (Skirycz andInzé, 2010; Osakabe et al, 2014)
To examine the contribution of the three GIBBERELLIN-INSENSITIVE DWARF1 (GID1) receptors to plant water status, we first compared the rate of water loss in M82 and all single and double gid1 mutants under water-deficit conditions
Relative water content (RWC) in M82, gid1b1, gid1b2 and gid1b1 gid1b2 was reduced by approximately 20%, while in gid1a, gid1a gid1b1 and gid1a gid1b2 RWC was similar to the irrigated plants (Fig. 1A)
Summary
Drought has a major impact on plant development and food supply, and is responsible for major losses of crop productivity (Mittler and Blumwald, 2010).Plants have adopted various strategies to cope with water deficiency, including maintaining water status by stomatal closure, accumulation of osmolytes and stress related proteins and changes in growth and development (Skirycz andInzé, 2010; Osakabe et al, 2014). Drought has a major impact on plant development and food supply, and is responsible for major losses of crop productivity (Mittler and Blumwald, 2010). Plants have adopted various strategies to cope with water deficiency, including maintaining water status by stomatal closure, accumulation of osmolytes and stress related proteins and changes in growth and development Expression of stress related genes and developmental changes in response to water deficiency are mediated primarily by the stress hormone abscisic acid (ABA; Cutler et al., 2010). Several studies suggested that the ABA-antagonist hormone, gibberellin (GA), has role in these responses (Colebrook et al 2014). GA regulates numerous developmental processes throughout the life cycle of the plant, from germination to fruit development (Davière and Achard, 2013).
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