College of Agronomy, Sichuan Agricultural University, Chengdu, Sichuan, 611130, China.
J Exp Bot. 2012 Oct;63(16):5979-89. doi: 10.1093/jxb/ers246.
Starch synthase I (SSI) contributes the majority of the starch synthase activity in developing maize endosperm. In this work, the effects of various plant hormones and sugars on the expression of the starch synthase I gene (ZmSSI) in developing maize endosperms were examined. The accumulation of ZmSSI mRNA was induced using abscisic acid (ABA) but not with glucose, sucrose, or gibberellin treatment. To investigate the molecular mechanism underlying this effect, the ZmSSI promoter region (-1537 to +51) was isolated and analysed. A transient expression assay in maize endosperm tissue showed that the full-length ZmSSI promoter is activated by ABA. The results of deletion and mutation assays demonstrated that a CACCG motif in the ZmSSI promoter is responsible for the ABA inducibility. The results of binding shift assays indicated that this CACCG motif interacts with the maize ABI4 protein in vitro. The overexpression of ABI4 in endosperm tissue enhanced the activity of a promoter containing the CACCG motif in the absence of ABA treatment. Expression pattern analysis indicated that the transcription pattern of ABI4 in the developing maize endosperm was induced by ABA treatment but was only slightly affected by glucose or sucrose treatment. Taken together, these data indicate that ABI4 binds to the CACCG motif in the ZmSSI promoter and mediates its ABA inducibility.
淀粉合酶 I（SSI）在玉米胚乳的发育过程中贡献了大部分的淀粉合酶活性。在这项工作中，研究了各种植物激素和糖对发育中的玉米胚乳中淀粉合酶 I 基因（ZmSSI）表达的影响。用脱落酸（ABA）诱导 ZmSSI mRNA 的积累，但葡萄糖、蔗糖或赤霉素处理则没有。为了研究这种效应的分子机制，分离并分析了 ZmSSI 启动子区（-1537 到+51）。在玉米胚乳组织中的瞬时表达分析表明，全长 ZmSSI 启动子被 ABA 激活。缺失和突变分析的结果表明，ZmSSI 启动子中的 CACCG 基序负责 ABA 的诱导性。结合移位分析的结果表明，该 CACCG 基序在体外与玉米 ABI4 蛋白相互作用。ABI4 在胚乳组织中的过表达增强了含有 CACCG 基序的启动子在没有 ABA 处理时的活性。表达模式分析表明，ABI4 在发育中的玉米胚乳中的转录模式被 ABA 处理诱导，但仅受葡萄糖或蔗糖处理的轻微影响。综上所述，这些数据表明 ABI4 结合到 ZmSSI 启动子中的 CACCG 基序，并介导其 ABA 的诱导性。
