GmMAX2-D14 and -KAI interaction-mediated SL and KAR signaling play essential roles in soybean root nodulation
GmMAX2-D14 and -KAI interaction-mediated SL and KAR signaling play essential roles in soybean root nodulation
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DOI：
10.1111/tpj.14545
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发表时间：
2019-11-14
期刊：
影响因子：
7.2
通讯作者：
Zhao, Jian
中科院分区：
文献类型：
--
作者：
Ahmad, Muhammad Zulfiqar;Rehman, Naveed Ur;Zhao, Jian
尽管植物生长发育、植物寄生和植物真菌相互作用中具有重要作用，但它们在大豆-根瘤菌相互作用中的作用尚不清楚。SL/KAR信号转导基因GmMAX2a、GmD14s和GmKAi被根瘤菌侵染激活。在GmMAX2a高表达突变体(GmMAX2a-OE)和基因敲除突变体(GmMAX2a-KD)中，GmMAX2a修复了atmax 2根毛缺陷，并改变了大豆根毛。GmMAX2a-KD产生的根瘤较少，而GmMAX2a-OE产生的根瘤比GUS毛状根多。GmMAX2a在其KD或OE转基因毛状根中的突变影响了根瘤菌感染诱导的早期结瘤基因表达的增加。两个突变的毛状根也表现出生长素、茉莉酸和脱落酸水平的变化，这一点通过对它们合成基因的转录分析进一步证实。生长素合成基因GmYUC2a的过表达也影响了SL和KAR信号基因。GmMAX2a与SL/KAR受体GmD14S、GmKAIs和GmD14L以不同的结合亲和力相互作用，这取决于关键氨基酸的变化，形成活性D14/KAI-SCFMAX2复合体。根瘤特异表达GmKAI和GmD14LS的敲除突变根产生的根瘤较少，几个早期结瘤基因的表达发生了变化。GmMAX2a突变体的根中GmKAIs和GmD14L的表达水平发生了显著变化，其靶抑制基因GmD53s和GmSMAX1s也发生了显著变化。因此，SL和KAR信号部分通过与激素的相互作用参与大豆-根瘤菌的相互作用和结瘤，这可能解释了MXA2同系物对豆科植物确定结瘤和不确定结瘤的不同影响。这项研究为GmMAX2介导的SL/KAR信号在大豆根毛和根瘤形成中的作用提供了新的见解。
Despite of important functions of strigolactones (SLs) and karrikins (KARs) in plant development, plant-parasite and plant-fungi interactions, their roles in soybean-rhizobia interaction remain elusive. SL/KAR signaling genes GmMAX2a, GmD14s, and GmKAIs are activated by rhizobia infection. GmMAX2a restored atmax2 root hair defects and soybean root hairs were changed in GmMAX2a overexpression (GmMAX2a-OE) or knockdown (GmMAX2a-KD) mutants. GmMAX2a-KD gave fewer, whereas GmMAX2a-OE produced more nodules than GUS hairy roots. Mutation of GmMAX2a in its KD or OE transgenic hairy roots affected the rhizobia infection-induced increases in early nodulation gene expression. Both mutant hairy roots also displayed the altered auxin, jasmonate and abscisic acid levels, as further verified by transcriptomic analyses of their synthetic genes. Overexpression of an auxin synthetic gene GmYUC2a also affected SL and KAR signaling genes. GmMAX2a physically interacted with SL/KAR receptors GmD14s, GmKAIs, and GmD14Ls with different binding affinities, depending on variations in the critical amino acids, forming active D14/KAI-SCFMAX2 complexes. The knockdown mutant roots of the nodule-specifically expressing GmKAIs and GmD14Ls gave fewer nodules, with altered expression of several early nodulation genes. The expression levels of GmKAIs, and GmD14Ls were markedly changed in GmMAX2a mutant roots, so did their target repressor genes GmD53s and GmSMAX1s. Thus, SL and KAR signaling were involved in soybean-rhizobia interaction and nodulation partly through interactions with hormones, and this may explain the different effects of MXA2 orthologs on legume determinate and indeterminate nodulation. The study provides fresh insights into the roles of GmMAX2-mediated SL/KAR signaling in soybean root hair and nodule formation.