Embrapa Soja, C.P. 231, 86001-970 Londrina, Paraná, Brazil.
Universidade Estadual de Londrina, Dept. Bioquímica e Biotecnologia, C.P. 60001, 86051-990, Londrina, Paraná, Brazil.
Microbiology (Reading). 2019 Sep;165(9):990-1000. doi: 10.1099/mic.0.000824. Epub 2019 Jun 11.
strain CIAT 899 possesses outstanding agronomic properties as it displays tolerance to environmental stresses, a broad host range and high effectiveness in fixing nitrogen with the common bean ( L.); in addition, it carries intriguing features such as five copies of the regulatory gene, and the capacity to synthesize a variety of nodulation factors (NFs), even in a flavonoid-independent manner, when submitted to abiotic stresses. However, the roles of several genes of the repertoire of CIAT 899 remain to be determined. In this study, we obtained mutants for the , and genes of CIAT 899 and investigated their expression, NF structures and symbiotic properties. Either in the presence of the flavonoid apigenin, or of salt the expression of , and in wild-type CIAT 899 was highly up-regulated in comparison to the mutants of all five copies of , indicating the roles that regulatory genes play in the activation of , and ; however, NodD1 was recognized as the main inducer. In total, 29 different NF structures were synthesized by wild-type CIAT 899 induced by apigenin, and 36 when induced by salt, being drastically reduced by mutations in , and , especially under osmotic stress, with specific changes related to each gene, indicating that the three genes participate in the synthesis of NFs. Mutations in , and affected differently symbiotic performance (nodule number and shoot dry weight), according to the host plant. Our results indicate that the expression of , and genes of CIAT 899 is mediated by genes, and although these three genes do not belong to the main set of genes controlling nodulation, they contribute to the synthesis of NFs that will impact symbiotic performance and host specificity.
菌株 CIAT 899 具有出色的农艺性状，因为它对环境胁迫具有耐受性，宿主范围广泛，并且在与普通豆（L.）共生固氮方面非常有效；此外，它具有引人注目的特征，例如 5 个调控基因的副本，以及在非生物胁迫下，即使在没有类黄酮的情况下，也能合成多种结瘤因子（NFs）的能力。然而，CIAT 899 基因库中的几个基因的作用仍有待确定。在这项研究中，我们获得了 CIAT 899 的 、 和 基因的突变体，并研究了它们的表达、NF 结构和共生特性。无论是在类黄酮芹菜素的存在下，还是在盐胁迫下，与所有 5 个 基因的突变体相比，野生型 CIAT 899 中 、 和 的表达都被高度上调，表明调控 基因在激活 、 和 中发挥作用；然而，NodD1 被认为是主要的诱导因子。总共，野生型 CIAT 899 在芹菜素诱导下合成了 29 种不同的 NF 结构，在盐诱导下合成了 36 种 NF 结构，在 、 和 突变体中急剧减少，特别是在渗透胁迫下，与每个基因相关的特定变化表明，这三个基因参与 NF 的合成。 、 和 基因的突变对不同宿主植物的共生表现（根瘤数和地上部干重）有不同的影响。我们的结果表明，CIAT 899 的 、 和 基因的表达是由 基因介导的，尽管这三个基因不属于控制结瘤的主要基因集，但它们有助于 NF 的合成，从而影响共生表现和宿主特异性。
