Huynh Christian A, Guinel Frédérique C
Department of Biology, Wilfrid Laurier University, Waterloo, ON N2K 3V3, Canada.
Plants (Basel). 2020 Nov 6;9(11):1505. doi: 10.3390/plants9111505.
E107 and E132 are pea mutants that nodulate poorly. Because they have a shoot-controlled nodulation phenotype, we asked if their mutated genes were implicated in the autoregulation of nodulation (AON), a mechanism which consists of two systemic circuits, the positive CEP/CRA2 and the negative CLE/SUNN, coordinated via NIN and miR2111. We further characterized the mutants' phenotype by studying nodule distribution and nodulation efficiency. E107 was similar to wild-type (WT) in its nodule distribution, but E132 had an extended nodulation zone with nodules forming distally on its lateral roots. Moreover, we tested whether their shoots produced a compound inhibitory to nodulation. We made ethyl-acetate extracts of roots and shoots of both mutants and WT, which we applied to rhizobia-inoculated WT seedlings and to pure rhizobial cultures. Whereas free-living bacteria were unaffected by any of the extracts, WT treated with shoot extracts from either inoculated mutant had fewer nodules than that of control. E107 and E132 shoot extracts led to a 50% and a 35% reduction in nodule number, respectively. We propose that E107 and E132 belong to a new sub-class of AON mutants, i.e., hypo-nodulators, and that their respective gene products are acting in the AON descending branch, upstream of TML signaling.
E107和E132是结瘤能力较差的豌豆突变体。由于它们具有受地上部控制的结瘤表型，我们探究其突变基因是否参与了结瘤自调控（AON），这一机制由两个系统回路组成，即正向的CEP/CRA2和负向的CLE/SUNN，通过NIN和miR2111进行协调。我们通过研究根瘤分布和结瘤效率进一步对突变体的表型进行了表征。E107在根瘤分布上与野生型（WT）相似，但E132的结瘤区域有所扩展，在其侧根的远端形成根瘤。此外，我们测试了它们的地上部是否产生了一种抑制结瘤的化合物。我们制备了两种突变体和WT的根和地上部的乙酸乙酯提取物，并将其应用于接种根瘤菌的WT幼苗和纯根瘤菌培养物。虽然自由生活的细菌不受任何提取物的影响，但用任一接种突变体的地上部提取物处理的WT结瘤数均少于对照。E107和E132地上部提取物分别使根瘤数减少了50%和35%。我们提出E107和E132属于AON突变体的一个新亚类，即结瘤不足突变体，并且它们各自的基因产物在AON下行分支中发挥作用，位于TML信号的上游。
