Serova Tatiana A, Tsyganova Anna V, Tsyganov Viktor E
All-Russia Research Institute for Agricultural Microbiology, Laboratory of Molecular and Cellular Biology, Podbelsky Chaussee 3, 196608, Pushkin 8, Saint-Petersburg, Russia.
Protoplasma. 2018 Sep;255(5):1443-1459. doi: 10.1007/s00709-018-1246-9. Epub 2018 Apr 3.
Plant symbiotic mutants are useful tool to uncover the molecular-genetic mechanisms of nodule senescence. The pea (Pisum sativum L.) mutants SGEFix-1 (sym40), SGEFix-3 (sym26), and SGEFix-7 (sym27) display an early nodule senescence phenotype, whereas the mutant SGEFix-2 (sym33) does not show premature degradation of symbiotic structures, but its nodules show an enhanced immune response. The nodules of these mutants were compared with each other and with those of the wild-type SGE line using seven marker genes that are known to be activated during nodule senescence. In wild-type SGE nodules, transcript levels of all of the senescence-associated genes were highest at 6 weeks after inoculation (WAI). The senescence-associated genes showed higher transcript abundance in mutant nodules than in wild-type nodules at 2 WAI and attained maximum levels in the mutant nodules at 4 WAI. Immunolocalization analyses showed that the ethylene precursor 1-aminocyclopropane-1-carboxylate accumulated earlier in the mutant nodules than in wild-type nodules. Together, these results showed that nodule senescence was activated in ineffective nodules blocked at different developmental stages in pea lines that harbor mutations in four symbiotic genes.
植物共生突变体是揭示根瘤衰老分子遗传机制的有用工具。豌豆（Pisum sativum L.）突变体SGEFix-1（sym40）、SGEFix-3（sym26）和SGEFix-7（sym27）表现出早期根瘤衰老表型，而突变体SGEFix-2（sym33）未表现出共生结构的过早降解，但其根瘤表现出增强的免疫反应。使用七个已知在根瘤衰老过程中被激活的标记基因，将这些突变体的根瘤相互比较，并与野生型SGE系的根瘤进行比较。在野生型SGE根瘤中，所有衰老相关基因的转录水平在接种后6周（WAI）时最高。在接种后2周时，衰老相关基因在突变体根瘤中的转录丰度高于野生型根瘤，并在接种后4周时在突变体根瘤中达到最高水平。免疫定位分析表明，乙烯前体1-氨基环丙烷-1-羧酸在突变体根瘤中比在野生型根瘤中积累得更早。总之，这些结果表明，在四个共生基因发生突变的豌豆品系中，处于不同发育阶段受阻的无效根瘤中，根瘤衰老被激活。
