OsEXPA4 and OsRWC3 are involved in asymmetric growth during gravitropic bending of rice leaf sheath bases |
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| Authors: | Liwei Hu Dayong Cui Steven Neill Weiming Cai |
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| Institution: | Institute of Plant Physiology and Ecology, Shanghai Institutes for Biological Sciences, Graduate School of Chinese Academy of Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China; Centre for Research in Plant Science, University of the West of England, Bristol BS16 1QY, United Kingdom |
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| Abstract: | Expression of an expansin gene ( OsEXPA4 ) and a plasma membrane aquaporin ( OsRWC3 ) were differentially induced in the abaxial (lower) side of rice leaf sheath bases during gravitropism. Expression of both of these genes was induced by GA3. β-glucuronidase (GUS) activity in transgenic rice expressing a GUS reporter gene under the control of the gibberellin (GA)-responsive OsRWC3 promoter was investigated during gravitropic curvature and found to be enhanced in the abaxial side of graviresponding leaf sheath bases. Ancymidol, a GA biosynthesis inhibitor, reduced the expression gradient of OsEXPA4 and OsRWC3 . The osmotic potential was transiently lower on the abaxial side of gravistimulated leaf sheath bases, and the gravitropic curvature was inhibited by HgCl2 and phloretin, two known inhibitors of aquaporins. These data suggest that asymmetric GA redistribution following gravistimulation results in the localized expression of OsEXPA4 and OsRWC3 , that in turn might bring about differential cell wall loosening, cell expansion and water influx via aquaporins, thus leading to gravitropic bending. |
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