A SOC1-like gene MtSOC1a promotes flowering and primary stem elongation in Medicago

First author: Mauren Jaudal; Affiliations: University of Auckland (新西兰奥克兰大学): Auckland, New Zealand

Corresponding author: Joanna Putterill

Medicago flowering, like Arabidopsis, is promoted by vernalisation (春化作用) and long days, but alternative mechanisms are predicted because Medicago lacks the key regulators CO and FLC. Three Medicago SOC1-like genes, including MtSOC1a, were previously implicated in flowering control, but no legume soc1mutants with altered flowering were reported. Here, RT-qPCR indicated that the timing and magnitude of MtSOC1a expression was regulated by the flowering promoter FTa1, while in situ hybridisation indicated that MtSOC1a expression increased in the shoot apical meristem during the floral transition. A Mtsoc1a mutant showed delayed flowering and short primary stems. Overexpression of MtSOC1a partially rescued the flowering of Mtsoc1a, but caused a dramatic increase in primary stem height, well before the transition to flowering. Internode cell length correlated with stem height, indicating that MtSOC1a promotes cell elongation in the primary stem. However, application of gibberellin (GA3) caused stem elongation in both wild type and Mtsoc1a, indicating the mutant was not defective in GA responsiveness. These results indicate that MtSOC1a may function as a floral integrator gene and promotes primary stem elongation. Overall, this study suggests that apart from some conservation with the Arabidopsis flowering network, MtSOC1a has a novel role in regulating aspects of shoot architecture.

苜蓿的开花与拟南芥类似，都是由春化作用和长日照所促进，但由于苜蓿中缺少关键调控蛋白CO和FLC，所以其具体的控制开花的分子机制还不清楚。已有的研究表明苜蓿的SOC1-like基因作用于开花调控，但是目前还未发现开花受到影响的soc突变体苜蓿植株。本文通过RT-qPCR显示MtSOC1a基因表达的时间和量级受到开花促进基因FTa1的调控，原位杂交显示成花转变时茎尖分生组织中的MtSOC1a基因表达量升高。Mtsoc1a突变体开花延迟，并且主茎缩短。过表达MtSOC1a基因能够部分恢复Mtsoc1a突变体的表型，但在进入开花之前植株主茎的高度显著增高。节间的细胞长度与茎的高度相关，说明MtSOC1a基因促进了主茎中的细胞伸长。然而，外施赤霉素GA3能够增加野生型和Mtsoc1a突变体的主茎高度，说明Mtsoc1a突变体在GA响应中不存在缺陷。这些结果揭示了MtSOC1a基因可能作为成花整合基因，并能够促进主茎的伸长。综上，本文的研究说明了除了具有与拟南芥保守的开花网络调控功能之外，苜蓿中MtSOC1a基因还可能在植株结构方面起到调控作用。

通讯：Joanna Putterill (https://unidirectory.auckland.ac.nz/profile/j-putterill)

研究方向：植物开花时间的分子调控机制。

doi: https://doi.org/10.1093/jxb/ery284

Journal: Journal of Experimental Botany

Published date: 26 July, 2018

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