Calcium (Ca 2+ ) signals are decoded by the Ca 2+ -sensor protein calmodulin (CaM) and are transduced to Ca 2+ /CaM-binding transcription factors to directly regulate gene expression necessary for acclimation responses in plants. The molecular mechanisms of Ca 2+ /CaM signal transduction processes and their functional significance remains enigmatic. Here we report a novel Ca 2+ /CaM signal transduction mechanism that allosterically regulates DNA-binding activity of GT2-LIKE 1 (GTL1), a transrepressor of STOMATAL DENSITY AND DISTRIBUTION 1 ( SDD1 ), to repress stomatal development in response to water stress. We demonstrated that Ca 2+ /CaM interaction with the 2 nd helix of the GTL1 N-terminal trihelix DNA-binding domain (GTL1N) destabilizes a hydrophobic core of GTL1N and allosterically inhibits 3 rd helix docking to the SDD1 promoter, leading to osmotic stress-induced Ca 2+ /CaM-dependent activation (de-repression) of SDD1 expression. This resulted in GTL1-dependent repression of stomatal development in response to water-deficit stress. Together, our results demonstrate that a Ca 2+ /CaM-regulated transcriptional switch on a trihelix transrepressor directly transduces osmotic stress to repress stomatal development to improve plant water-use efficiency as an acclimation response.
SummaryWe have identified a novel means to achieve substantially increased vegetative biomass and oilseed production in the model plant Arabidopsis thaliana. Endogenous isoforms of starch branching enzyme (SBE) were substituted by either one of the endosperm-expressed maize (Zea mays L.) branching isozymes, ZmSBEI or ZmSBEIIb. Transformants were compared with the starch-free background and with the wild-type plants. Each of the maize-derived SBEs restored starch biosynthesis but both morphology and structure of starch particles were altered. Altered starch metabolism in the transformants is associated with enhanced biomass formation and more-than-trebled oilseed production while maintaining seed oil quality. Enhanced oilseed production is primarily due to an increased number of siliques per plant whereas oil content and seed number per silique are essentially unchanged or even modestly decreased. Introduction of cereal starch branching isozymes into oilseed plants represents a potentially useful strategy to increase biomass and oilseed production in related crops and manipulate the structure and properties of leaf starch.
The stomata on leaf surfaces control gas exchange and water loss, closing during dry periods to conserve water. The distribution and size of stomatal complexes is determined by epidermal cell differentiation and expansion during leaf growth. Regulation of these processes in response to water deficit may result in stomatal anatomical plasticity as part of the plant acclimation to drought. We quantified the leaf anatomical plasticity under water-deficit conditions in maize and soybean over two experiments. Both species produced smaller leaves in response to the water deficit, partly due to the reductions in the stomata and pavement cell size, although this response was greater in soybean, which also produced thicker leaves under severe stress, whereas the maize leaf thickness did not change. The stomata and pavement cells were smaller with the reduced water availability in both species, resulting in higher stomatal densities. Stomatal development (measured as stomatal index, SI) was suppressed in both species at the lowest water availability, but to a greater extent in maize than in soybean. The result of these responses is that in maize leaves, the stomatal area fraction (fgc) was consistently reduced in the plants grown under severe but not moderate water deficit, whereas the fgc did not decrease in the water-stressed soybean leaves. The water deficit resulted in the reduced expression of one of two (maize) or three (soybean) SPEECHLESS orthologs, and the expression patterns were correlated with SI. The vein density (VD) increased in both species in response to the water deficit, although the effect was greater in soybean. This study establishes a mechanism of stomatal development plasticity that can be applied to other species and genotypes to develop or investigate stomatal development plasticity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.