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Aquaporin AtTIP5;1 as an essential target of gibberellins promotes hypocotyl cell elongation in Arabidopsis thaliana under excess boron stress
Aquaporins play essential roles in growth and development including stem elongation in plants. Tonoplast aquaporin AtTIP5;1 has been addressed to positively regulate hypocotyl elongation under high concentration of H3BO3 (HB) in Arabidopsis thaliana (L.) Heynh. However, the mechanism underlying this process remains unanswered. Here, we show that paclobatrazol (PAC), an inhibitor of gibberellins (GAs) biosynthesis, significantly suppressed the hypocotyl cell elongation of WT, and more strongly suppressed that of AtTIP5;1 overexpressors under HB stress. Two AtTIP5;1 null mutants displayed arrested elongation of cells in the upper part of hypocotyls compared with WT in the presence of HB or GA3. Moreover, PAC treatment completely inhibited the increases in AtTIP5;1 transcripts induced by HB, while GA3 application evidently upregulated AtTIP5;1 expression in WT. In addition, treatment with HB remarkably elevated the expression levels of GA3ox1、GA20ox1 and GA20ox2, key biosynthesis genes of GAs, in WT seedlings. The contents of GA3 and GA4 also increased in WT seedlings grown in HB-contained MS medium. Besides, application of HB failed to enhance AtTIP5;1 expression in the double mutant rga-24/gai-t6 of DELLA genes. Together, these results suggest that AtTIP5;1 is an essential downstream target of GAs. HB induces the accumulation of GAs, which activates AtTIP5;1 through modulation of DELLA protein RGA and GAI, further promoting hypocotyl elongation in Arabidopsis thaliana.
FP16444 Accepted 29 August 2017
© CSIRO 2017