生长素介导OsRGP1和OsSuS参与水稻地上部基部向重性弯曲生长(英文)

AUXIN-REGULATED OsRGP1 AND OsSuS ARE INVOLVED IN GRAVITROPIC BENDING OF RICE SHOOT BASES

在水稻幼苗被放平后,地上部重力响应部位(地上部基部)的上半部生长比下半部生长慢,从而导致地上部基部发生向上弯曲,发生不对称生长的向重性反应。通过抑制差减杂交(SSH)实验发现,水稻地上部基部向重性弯曲生长过程中,反复糖基化多肽OsRGP1和蔗糖合成酶OsSuS在基部上下部有不对称表达。我们还采用Realtime PCR开展进一步研究。实验结果显示OsRGP1和OsSuS的表达受到IAA的调控。通过生物信息学分析也发现OsRGP1和OsSuS的启动子上存在着生长素的调控元件,生长素极性运输抑制剂TIBA处理能够消除OsRGP1和OsSuS在向重性过程中的不对称表达,这进一步说明向重性过程中不对称分布的生长素介导了OsRGP1和OsSuS基因的不对称表达。另外,向重性反应过程中,检测到基部下半部的己糖浓度增加。因此,OsRGP1的不对称表达可能有助于下半部细胞壁多糖的积累,进而促进了下半部细胞壁的扩张。OsSuS不对称表达也有可能会引起己糖在上下半部的不对称分布。己糖和细胞壁多糖在下半部的积累可能在下部细胞扩张从而导致向重性弯曲生长中起一定的作用。

Gravitropie bending of horizontally-oriented rice shoots results from the differential elongation of cells in the upper and lower halves of the shoot bases. In this study, genes encoding a reversibly glycosylated polypeptide （OsRGP1） and a sucrose synthase （OsSuS） related to sugar metabolism were identified by suppressive subtractive hybridization （SSH） as being differentially expressed in gravibending lower and upper halves of rice shoot bases. RT-PCR was used to monitor OsRGP1 and OsSuS gene expression. The two genes were differentially induced in lower and upper halves of the shoot bases during gravitropism and their expression was regulated by auxin. Gene promoter sequence analysis demonstrated the existence of elements related to auxin. Treatment with the auxin transport inhibitor TIBA inhibited the asymmetric expression of OsRGP1 and OsSuS. In addition, an increase in hexose sugars was detected in the lower half of the shoot bases during gravitropism. Our data suggest that asymmetric redistribution of auxin following gravistimulation results in differentially localized OsRGP1 and OsSuS expression. While asymmetric expression of OsSuS may result in a disproportionate distribution of hexose, asymmetric expression of OsRGP1 could induce cell wall polysaccharide synthesis in the lower half of shoot bases. Therefore hexose and cell wall polysaccharide accumulation in the lower half of rice shoot bases might contribute to cell expansion and subsequent gravitropic bending.