State Key Laboratory of Silkworm Genome Biology, Southwest University, Beibei, Chongqing, 400715, P. R. China.
Sci Rep. 2018 Apr 11;8(1):5860. doi: 10.1038/s41598-018-23985-0.
The MADS-box genes encode transcriptional regulators with various functions especially during floral development. A total of 54 putative Morus notabilis MADS-box genes (MnMADSs) were identified and phylogenetically classified as either type I (17 genes) or type II (37 genes). The detected genes included three FLOWERING LOCUS C-like (MnFLC-like) genes, MnMADS33, MnMADS50, and MnMADS7. MnFLC-like proteins could directly or indirectly repress promoter activity of the mulberry FLOWERING LOCUS T-like (MnFT) gene. Transgenic Arabidopsis thaliana overexpressing MnFLC-like genes exhibited delayed flowering and down-regulated expression of FT and SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1 (SOC1). The gene expression analyses in floral bud indicated that MnMADS33 expression increased, while MnFT expression decreased during the induction of dormancy in response to cold conditions. Dormancy release resulted in the down-regulation of MnMADS33 expression and the up-regulation of MnFT expression. Furthermore, abscisic acid promoted the transcription of MnMADS33 and MnFT, although the expression level of MnFT gradually decreased. These results are consistent with the hypothesis that MnMADS33 negatively regulated the expression of MnFT to repress dormancy release and flowering in mulberry. This study may be relevant for future investigations regarding the effects of MnMADS genes on mulberry flowering development.
MADS -box 基因编码具有多种功能的转录调控因子，尤其在花发育过程中发挥重要作用。本研究共鉴定到 54 个推测的野桑蚕 MADS-box 基因（MnMADSs），并根据系统进化关系将其分为 I 型（17 个基因）和 II 型（37 个基因）。所检测到的基因包括 3 个 FLOWERING LOCUS C 类（MnFLC-like）基因 MnMADS33、MnMADS50 和 MnMADS7。MnFLC-like 蛋白可以直接或间接抑制桑树 FLOWERING LOCUS T 类（MnFT）基因的启动子活性。过表达 MnFLC-like 基因的拟南芥转基因植株表现出开花延迟，并且 MnFT 和 SUPPRESSOR OF OVEREXPRESSION OF CONSTANS1（SOC1）的表达下调。在花芽中进行的基因表达分析表明，MnMADS33 的表达增加，而 MnFT 的表达在冷诱导休眠过程中降低。休眠解除导致 MnMADS33 的表达下调和 MnFT 的表达上调。此外，脱落酸促进了 MnMADS33 和 MnFT 的转录，尽管 MnFT 的表达水平逐渐降低。这些结果与 MnMADS33 负调控 MnFT 表达以抑制桑树休眠解除和开花的假说一致。本研究可能有助于未来研究 MnMADS 基因对桑树开花发育的影响。
