Department of Plant Systems Biology, VIB, 9052 Gent, Belgium.
Department of Plant Biotechnology and Genetics, Ghent University, 9052 Gent, Belgium.
New Phytol. 2011 Aug;191(3):647-661. doi: 10.1111/j.1469-8137.2011.03719.x. Epub 2011 Apr 19.
• Legume roots develop two types of lateral organs, lateral roots and nodules. Nodules develop as a result of a symbiotic interaction with rhizobia and provide a niche for the bacteria to fix atmospheric nitrogen for the plant. • The Arabidopsis NAC1 transcription factor is involved in lateral root formation, and is regulated post-transcriptionally by miRNA164 and by SINAT5-dependent ubiquitination. We analyzed in Medicago truncatula the role of the closest NAC1 homolog in lateral root formation and in nodulation. • MtNAC1 shows a different expression pattern in response to auxin than its Arabidopsis homolog and no changes in lateral root number or nodulation were observed in plants affected in MtNAC1 expression. In addition, no interaction was found with SINA E3 ligases, suggesting that post-translational regulation of MtNAC1 does not occur in M. truncatula. Similar to what was found in Arabidopsis, a conserved miR164 target site was retrieved in MtNAC1, which reduced protein accumulation of a GFP-miR164 sensor. Furthermore, miR164 and MtNAC1 show an overlapping expression pattern in symbiotic nodules, and overexpression of this miRNA led to a reduction in nodule number. • This work suggests that regulatory pathways controlling a conserved transcription factor are complex and divergent between M. truncatula and Arabidopsis.
豆科植物的根会发育出两种侧生器官，即侧根和根瘤。根瘤是根与根瘤菌共生的结果，为细菌固定大气中的氮提供了场所，从而为植物提供氮素。
拟南芥 NAC1 转录因子参与侧根的形成，其转录后水平受到 miRNA164 和 SINAT5 依赖性泛素化的调控。我们在蒺藜苜蓿中分析了与拟南芥 NAC1 同源的基因在侧根形成和根瘤形成中的作用。
与拟南芥同源物相比，MtNAC1 对生长素的表达模式不同，并且在 MtNAC1 表达受影响的植物中，侧根数量或根瘤形成没有变化。此外，没有发现与 SINA E3 连接酶的相互作用，这表明 MtNAC1 的翻译后调控在蒺藜苜蓿中不会发生。与在拟南芥中发现的情况类似，在 MtNAC1 中检索到一个保守的 miR164 靶位点，该位点减少了 GFP-miR164 传感器的蛋白积累。此外，miR164 和 MtNAC1 在共生根瘤中表现出重叠的表达模式，过表达这种 miRNA 会导致根瘤数量减少。
这项工作表明，在蒺藜苜蓿和拟南芥之间，调控保守转录因子的调控途径是复杂和不同的。
