Functional Analysis of Water Stress-Responsive Soybean GmNAC003 and GmNAC004 Transcription Factors in Lateral Root Development in Arabidopsis

Abstract

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.

Genome-Wide Identification and Expression Analysis of the CaNAC Family Members in Chickpea during Development, Dehydration and ABA Treatments

“…Thus, CaNAC67 being induced the most highly in both tissues is a promising candidate gene which deserves further and in-depth in planta molecular and functional analyses under drought. A number of studies have indicated that TF encoding genes with high inducibility by stress are preferable for selections of further in planta functional studies as they might have potential for development of improved stress-tolerant transgenic plants by overexpression approach [58] , [66] . Additionally, the repression degree of CaNAC s in dehydrated roots versus dehydrated leaves was also lower by approximately 4-fold.…”

A GmSIN1/GmNCED3s/GmRbohBs Feed-Forward Loop Acts as a Signal Amplifier That Regulates Root Growth in Soybean Exposed to Salt Stress

“…Glyma. 12G221500 (GmNAC004) and its homologs in the legume Caragana intermedia were recently reported to improve lateral root formation and caused insensitivity to ABA in seed germination when overexpressed in transgenic Arabidopsis (Quach et al, 2014;Han et al, 2015). However, improved primary root elongation under normal and salt stress conditions in 35S pro :GmSIN1 transgenic soybeans was not reported (Figure 1).…”

Synthetic strategies for plant signalling studies: molecular toolbox and orthogonal platforms

“…A further limitation of using Arabidopsis is exemplified in the case of the characterization of the soybean GmNAC004 (NAM, ATAF1/2, CUC1 domains) transcription factor in its role as a stimulant of lateral root development upon water deficit by Quach et al . (): constitutive expression of GmNAC004 in Arabidopsis did not lead to lateral root development in response to water deficit, as observed in soybean. Indeed in Arabidopsis, water deficiency represses the overall plant development, thus not showing the same stress response as in soybean.…”