Abscisic acid (ABA) levels increase significantly in plants under stress conditions, and ABA is thought to serve as a key stressresponse regulator. However, the direct effect of ABA on photosynthesis and the effect of mesophyll ABA on yield under both well-watered and drought conditions are still the subject of debate. Here, we examined this issue using transgenic Arabidopsis (Arabidopsis thaliana) plants carrying a dominant ABA-signaling inhibitor under the control of a mesophyll-specific promoter (FBPase::abi1-1, abbreviated to fa). Under normal conditions, fa plants displayed slightly higher stomatal conductance and carbon assimilation than wild-type plants; however, these parameters were comparable following ABA treatment. These observations suggest that ABA does not directly inhibit photosynthesis in the short term. The fa plants also exhibited a variety of altered phenotypes under optimal conditions, including more vigorous initial growth, earlier flowering, smaller flowers, and delayed chlorophyll degradation. Furthermore, under optimal conditions, fa plant seed production was less than a third of that observed for the wild type. However, under drought conditions, wild-type and fa seed yields were similar due to a significant reduction in wild-type seed and no reduction in fa seed. These findings suggest that endogenous basal ABA inhibits a stress-escape response under nonstressed conditions, allowing plants to accumulate biomass and maximize yield.
Bibliographical noteFunding Information:
1This work was supported by the Israel Ministry of Agriculture and Rural Development (Eugene Kandel Knowledge centers) as part of the “Root of the Matter” — The root zone knowledge center for leveraging modern agriculture; the Israel Science Foundation (ISF) (grant no. 876/16); and the United States-Israel Binational Science Foundation (BSF) (grant no. 2015100). 2These authors contributed equally to this work. 3Author for contact: email@example.com. 4Senior author. The author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.plantphysiol.org) is: Menachem Moshelion (firstname.lastname@example.org). B.N., A.Y., and M.M. planned and designed the research; B.N., A.Y., and G.K. performed the experiments; B.N., A.Y., and Y.Z. analyzed the data; B.N. and M.M. wrote the manuscript. [OPEN]Articles can be viewed without a subscription. www.plantphysiol.org/cgi/doi/10.1104/pp.18.01334
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