Dual involvement of a Medicago truncatula NAC transcription factor in root abiotic stress response and symbiotic nodule senescence
Dual involvement of a Medicago truncatula NAC transcription factor in root abiotic stress response and symbiotic nodule senescence
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DOI：
10.1111/j.1365-313x.2011.04859.x
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发表时间：
2012-04-01
期刊：
影响因子：
7.2
通讯作者：
Frugier, Florian
中科院分区：
文献类型：
--
作者：
de Zelicourt, Axel;Diet, Anouck;Frugier, Florian
与模式植物蒺藜苜蓿（Medicago truncatula）相关的豆科作物可以通过分枝和与根瘤菌建立共生关系以形成固氮根瘤来使其根系结构适应环境条件。土壤盐分是影响植物产量和根系生长的主要非生物胁迫。先前的转录组学分析确定了与蒺藜草根对盐胁迫的响应相关的几个转录因子，包括NAC（NAM/ATAF/CUC）编码基因。这些转录因子之一，MtNAC 969的过表达，诱导形成一个较短的和少分支的根系，而RNAi介导的MtNAC 969失活促进侧根的形成。过量表达植物的改变的根系能够在高盐下维持其生长，并且其中MtNAC 969下调的根在盐胁迫下显示出改善的生长。因此，盐胁迫标记物的表达分别在MtNAC 969过表达或RNAi根中降低或诱导，表明该转录因子在盐胁迫响应中的抑制功能。MtNAC 969在中央共生根瘤组织中的表达由硝酸盐处理诱导，并且在根和根瘤中受到盐的拮抗作用，类似于衰老标记。MtNAC 969 RNAi结节在固氮区积累造淀粉体，并且过早衰老。因此，MtNAC 969转录因子在根和根瘤中受环境线索的不同影响，参与控制蒺藜苜蓿根系对环境的适应的几种途径。
Legume crops related to the model plant Medicago truncatula can adapt their root architecture to environmental conditions, both by branching and by establishing a symbiosis with rhizobial bacteria to form nitrogen-fixing nodules. Soil salinity is a major abiotic stress affecting plant yield and root growth. Previous transcriptomic analyses identified several transcription factors linked to the M.truncatula response to salt stress in roots, including NAC (NAM/ATAF/CUC)-encoding genes. Over-expression of one of these transcription factors, MtNAC969, induced formation of a shorter and less-branched root system, whereas RNAi-mediated MtNAC969 inactivation promoted lateral root formation. The altered root system of over-expressing plants was able to maintain its growth under high salinity, and roots in which MtNAC969 was down-regulated showed improved growth under salt stress. Accordingly, expression of salt stress markers was decreased or induced in MtNAC969 over-expressing or RNAi roots, respectively, suggesting a repressive function for this transcription factor in the salt-stress response. Expression of MtNAC969 in central symbiotic nodule tissues was induced by nitrate treatment, and antagonistically affected by salt in roots and nodules, similarly to senescence markers. MtNAC969 RNAi nodules accumulated amyloplasts in the nitrogen-fixing zone, and were prematurely senescent. Therefore, the MtNAC969 transcription factor, which is differentially affected by environmental cues in root and nodules, participates in several pathways controlling adaptation of the M.truncatula root system to the environment.