Quach Truyen N, Tran Lam-Son Phan, Valliyodan Babu, Nguyen Hanh Tm, Kumar Rajesh, Neelakandan Anjanasree K, Guttikonda Satish Kumar, Sharp Robert E, Nguyen Henry T
Division of Plant Sciences, National Center for Soybean Biotechnology and Interdisciplinary Plant Group, University of Missouri, Columbia, Missouri, United States of America.
PLoS One. 2014 Jan 23;9(1):e84886. doi: 10.1371/journal.pone.0084886. eCollection 2014.
In Arabidopsis, NAC (NAM, ATAF and CUC) transcription factors have been found to promote lateral root number through the auxin signaling pathway. In the present study, the role of water stress-inducible soybean GmNAC003 and GmNAC004 genes in the enhancement of lateral root development under water deficit conditions was investigated. Both genes were highly expressed in roots, leaves and flowers of soybean and were strongly induced by water stress and moderately induced by a treatment with abscisic acid (ABA). They showed a slight response to treatment with 2,4-dichlorophenoxyacetic acid (2,4-D). The transgenic Arabidopsis plants overexpressing GmNAC004 showed an increase in lateral root number and length under non-stress conditions and maintained higher lateral root number and length under mild water stress conditions compared to the wild-type (WT), while the transgenic plants overexpressing GmNAC003 did not show any response. However, LR development of GmNAC004 transgenic Arabidopsis plants was not enhanced in the water-stressed compared to the well-watered treatment. In the treatment with ABA, LR density of the GmNAC004 transgenic Arabidopsis was less suppressed than that of the WT, suggesting that GmNAC004 counteracts ABA-induced inhibition of lateral root development. In the treatment with 2,4-D, lateral root density was enhanced in both GmNAC004 transgenic Arabidopsis and WT plants but the promotion was higher in the transgenic plants. Conversely, in the treatment with naphthylphthalamic acid (NPA), lateral root density was inhibited and there was no difference in the phenotype of the GmNAC004 transgenic Arabidopsis and WT plants, indicating that auxin is required for the action of GmNAC004. Transcript analysis for a number of known auxin and ABA related genes showed that GmNAC004's role may suppress ABA signaling but promote auxin signaling to increase lateral root development in the Arabidopsis heterologous system.
在拟南芥中，已发现NAC（NAM、ATAF和CUC）转录因子通过生长素信号通路促进侧根数量。在本研究中，对水分胁迫诱导的大豆GmNAC003和GmNAC004基因在水分亏缺条件下增强侧根发育中的作用进行了研究。这两个基因在大豆的根、叶和花中均高度表达，并受到水分胁迫的强烈诱导以及脱落酸（ABA）处理的中度诱导。它们对2,4-二氯苯氧乙酸（2,4-D）处理表现出轻微反应。与野生型（WT）相比，过表达GmNAC004的转基因拟南芥植株在非胁迫条件下侧根数量和长度增加，在轻度水分胁迫条件下保持较高的侧根数量和长度，而过表达GmNAC003的转基因植株未表现出任何反应。然而，与充分浇水处理相比，水分胁迫下GmNAC004转基因拟南芥植株的侧根发育并未增强。在ABA处理中，GmNAC004转基因拟南芥的侧根密度受到的抑制比WT小，这表明GmNAC004可抵消ABA诱导的侧根发育抑制。在2,4-D处理中，GmNAC004转基因拟南芥和WT植株的侧根密度均增加，但转基因植株中的促进作用更高。相反，在萘基邻苯二甲酸（NPA）处理中，侧根密度受到抑制，GmNAC004转基因拟南芥和WT植株的表型没有差异，这表明生长素是GmNAC004发挥作用所必需的。对一些已知的生长素和ABA相关基因的转录分析表明，GmNAC004的作用可能是抑制ABA信号传导，但促进生长素信号传导，以增加拟南芥异源系统中的侧根发育。
