2012年6月8日，杂志《The Plant Cell》在线发表了中国科学院遗传与发育生物学研究所储成才课题组童红宁博士的最新研究成果。这篇题为“DWARF AND LOW-TILLERING Acts as a Direct Downstream Target of a GSK3/SHAGGY-Like Kinase to Mediate Brassinosteroid Responses in Rice ”的论文（DOI:10.1105/tpc.112.097394），揭示了水稻中GSK2与DLT相互作用介导的BR信号传导的分子及生化机制。

油菜素内酯（BR）是一类重要的植物激素，参与植物生长发育的各个方面，其在调控植物株型、器官大小及抗病抗逆等过程中的功能决定了BR在生产上具有巨大的应用潜力，然而其在粮食作物中的信号传导机制的研究仍知之甚微。

通过大规模筛选水稻突变体，获得一个BR不敏感材料，并通过图位克隆方法克隆到相应基因DLT。DLT编码一个植物特异的GRAS蛋白家族成员，为水稻BR信号传导中一个新的关键正调控因子（Tong et al., Plant Journal 58: 803816, 2009）。进一步研究发现，DLT作为转录因子，可能为水稻中GSK3/SHAGGY-like激酶的直接底物，童红宁博士克隆了该激酶基因，命名为GSK2。分子、生理、生化及遗传等技术证明，GSK2为BR信号传导中的一个关键负调控子，通过与DLT直接相互作用对其磷酸化来调控DLT的蛋白水平及活性。

论文摘要：

In Arabidopsis thaliana, the GSK3/SHAGGY-like kinase BRASSINOSTEROID-INSENSITIVE2 (BIN2) plays a critical role in the brassinosteroid (BR) signaling pathway by negatively regulating the activities of bri1-EMS-SUPPRESSOR1/BRASSINAZOLE-RESISTANT1 family transcription factors that regulate the expression of downstream BR-responsive genes. In this study, we analyzed the function of a rice (Oryza sativa) GSK3/SHAGGY-like kinase (GSK2), which is one of the orthologs of BIN2. Overexpression of GSK2 (Go) led to plants with typical BR loss-of-function phenotypes, and suppression of GSK2 resulted in enhanced BR signaling phenotypes. DWARF AND LOW-TILLERING (DLT) is a positive regulator that mediates several BR responses in rice. Suppression of DLT can enhance the phenotypes of BR receptor mutant d61-1, and overexpression of DLT obviously suppressed the BR loss-of-function phenotypes of both d61-1 and Go, suggesting that DLT functions downstream of GSK2 to modulate BR responses. Indeed, GSK2 can interact with DLT and phosphorylate DLT. Moreover, brassinolide treatment can induce the dephosphorylation of DLT, leading to the accumulation of dephosphorylated DLT protein. In GSK2 transgenic plants, the DLT phosphorylation level is dictated by the GSK2 level. These results demonstrate that DLT is a GSK2 substrate, further reinforcing that the BIN2/GSK2 kinase has multiple substrates that carry out various BR responses.

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