79.キュウリの芽ばえのペグ形成領域で発現するPINオーキシン排出キャリア相同遺伝子の同定と局在解析(口頭発表)

概要

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In Cucurbitaceae plants, a protuberance called a peg is formed on the transition zone between the hypocotyl and the root. When cucumber seeds germinate in a horizontal position, a peg forms on the lower side of the transition zone. We have suggested that auxin efflux is required for the differential decrease in auxin level in the gravistimulated transition zone of cucumber. To reveal a mechanism underlying the gravity-controlled peg formation, it is important to identify auxin efflux facilitators that are expressed in endodermis of the transition zone of cucumber seedlings. In this study, we isolated cDNAs encoding PIN auxin efflux facilitator family protein (CsPIN1? CsPIN6) from cucumber and examined the corresponding mRNA accumulation in the transition zone of cucumber seedlings. Our results of in situ hybridization indicate that CsPIN1, CsPIN4 and CsPIN6 mRNAs accumulate abundantly in endodermis/xylem, xylem and phloem cells of the transition zone, respectively. Furthermore, immunohistochemical staining with anti-CsPIN1 antibodies produced signals in vascular tissues and endodermis. Because endodermal cells have been reported to be responsible for sensing gravity for the lateral placement of the peg, CsPIN1 in endodermis could contribute to auxin redistribution that ultimately causes the suppression of peg formation on the upper side of the gravistimulated seedlings of cucumber.
2008-10-06