PDF(Pubmed)
Abstract：
In this study, the roles of glutathione (GSH), homoglutathione (hGSH), and their ratio in symbiotic nodule development and functioning, as well as in defense responses accompanying ineffective nodulation in pea (Pisum sativum) were investigated. The expression of genes involved in (h)GSH biosynthesis, thiol content, and localization of the reduced form of GSH were analyzed in nodules of wild-type pea plants and mutants sym33-3 (weak allele, \"locked\" infection threads, occasional bacterial release, and defense reactions) and sym33-2 (strong allele, \"locked\" infection threads, defense reactions), and sym40-1 (abnormal bacteroids, oxidative stress, early senescence, and defense reactions). The effects of (h)GSH depletion and GSH treatment on nodule number and development were also examined. The GSH:hGSH ratio was found to be higher in nodules than in uninoculated roots in all genotypes analyzed, with the highest value being detected in wild-type nodules. Moreover, it was demonstrated, that a hGSHS-to-GSHS switch in gene expression in nodule tissue occurs only after bacterial release and leads to an increase in the GSH:hGSH ratio. Ineffective nodules showed variable GSH:hGSH ratios that correlated with the stage of nodule development. Changes in the levels of both thiols led to the activation of defense responses in nodules. The application of a (h)GSH biosynthesis inhibitor disrupted the nitrogen fixation zone in wild-type nodules, affected symbiosome formation in sym40-1 mutant nodules, and meristem functioning and infection thread growth in sym33-3 mutant nodules. An increase in the levels of both thiols following GSH treatment promoted both infection and extension of defense responses in sym33-3 nodules, whereas a similar increase in sym40-1 nodules led to the formation of infected cells resembling wild-type nitrogen-fixing cells and the disappearance of an early senescence zone in the base of the nodule. Meanwhile, an increase in hGSH levels in sym40-1 nodules resulting from GSH treatment manifested as a restriction of infection similar to that seen in untreated sym33-3 nodules. These findings indicated that a certain level of thiols is required for proper symbiotic nitrogen fixation and that changes in thiol content or the GSH:hGSH ratio are associated with different abnormalities and defense responses.
摘要：
在这项研究中,谷胱甘肽（GSH）的作用，同型谷胱甘肽（hGSH），以及它们在共生结节发育和功能中的比例，以及伴随豌豆（Pisumsativum）无效结瘤的防御反应。参与（h）GSH生物合成的基因的表达，硫醇含量，在野生型豌豆植物和突变体sym33-3（弱等位基因，“锁定”感染线程，偶尔释放细菌，和防御反应）和sym33-2（强等位基因，“锁定”感染线程，防御反应)，和sym40-1（异常类细菌，氧化应激，早期衰老，和防御反应)。还检查了（h）GSH耗竭和GSH处理对结节数量和发育的影响。在分析的所有基因型中，结节中的GSH：hGSH比率均高于未接种的根中，在野生型结节中检测到最高值。此外，它被证明，结节组织中基因表达的hGSHS到GSHS转换仅在细菌释放后发生，并导致GSH：hGSH比率增加。无效结节显示出可变的GSH：hGSH比率，与结节发育阶段相关。两种硫醇水平的变化导致结核中防御反应的激活。（h）GSH生物合成抑制剂的应用破坏了野生型结节的固氮区，影响了sym40-1突变结节中的共生体形成，以及sym33-3突变结节中的分生组织功能和感染线生长。GSH治疗后两种硫醇水平的增加促进了sy33-3结节的感染和防御反应的扩展，而sym40-1结节的类似增加导致形成类似于野生型固氮细胞的感染细胞，并在结节底部消失了早期衰老区。同时,由GSH治疗引起的sy40-1结节中hGSH水平的增加表现为与未治疗的sy33-3结节相似的感染限制。这些发现表明，适当的共生固氮需要一定水平的硫醇，并且硫醇含量或GSH：hGSH比率的变化与不同的异常和防御反应有关。
