オーキシンによる植物の重力形態形成の制御機構に関する研究(受賞業績)

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Cucumber seedlings develop a protuberance called peg on the transition zone between the hypocotyl and the root. The lateral placement of a peg occurs because peg formation on upper side of the horizontally placed transition zone is suppressed in response to gravity. Reduction of auxin level on the upper side of the transition zone is responsible for the suppression of peg formation. We isolated six cDNAs encoding auxin efflux facilitators (CsPINs) in cucumber, and showed that CsPIN1 and CsPIN6 could control auxin dynamics for the gravimorphogenesis. Of auxin response factors (CsARFs) we isolated, CsARF2 and CsARF5 appeared to function on the auxin-mediated transcription as positive and negative regulators, respectively. CsIAA1 and CsIAA2 belonging to Aux/IAA family appeared to be negative regulators for the transcription. Furthermore, an auxin-inducible gene, CS-ACS1, was differentially expressed in the gravistimulated transition zone, which could cause an increase in ethylene production to promote peg development on the lower side. In addition, we found that mRNA of glycine-rich protein (CsGRP1) accumulated more abundantly on the upper side than the lower side of the transition zone. CsGRP1 gene was auxin-repressive, and the transition zone responded to gravistimulation in a specific manner by an asymmetric expression of CsGRP1 gene. Based on the results of these studies, we hypothesized the mechanism underlying the negative control of peg formation by gravity.
2009-05-31

オーキシンによる植物の重力形態形成の制御機構に関する研究(受賞業績)

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