Abstract
Abiotic stresses are major environmental factors that affect agricultural productivity worldwide. NAC transcription factors play pivotal roles in abiotic stress signaling in plants. As a staple crop, wheat production is severely constrained by abiotic stresses whereas only a few NAC transcription factors have been characterized functionally. To promote the application of NAC genes in wheat improvement by biotechnology, a novel NAC gene designated TaNAC67 was characterized in common wheat. To determine its role, transgenic Arabidopsis overexpressing TaNAC67-GFP controlled by the CaMV-35S promoter was generated and subjected to various abiotic stresses for morphological and physiological assays. Gene expression showed that TaNAC67 was involved in response to drought, salt, cold and ABA treatments. Localization assays revealed that TaNAC67 localized in the nucleus. Morphological analysis indicated the transgenics had enhanced tolerances to drought, salt and freezing stresses, simultaneously supported by enhanced expression of multiple abiotic stress responsive genes and improved physiological traits, including strengthened cell membrane stability, retention of higher chlorophyll contents and Na+ efflux rates, improved photosynthetic potential, and enhanced water retention capability. Overexpression of TaNAC67 resulted in pronounced enhanced tolerances to drought, salt and freezing stresses, therefore it has potential for utilization in transgenic breeding to improve abiotic stress tolerance in crops.
Highlights
Crop plants constantly encounter unfavorable environmental conditions, including drought, high salinity, and extreme temperatures, that significantly affect both biomass and grain yield worldwide
TaNAC67 fell into the stress-responsive NAC group based on the conserved NAC domain, and a highly conserved motif possibly involved in DNA binding was identified in the NAC domain (74-105AA) (Fig. 1A) [11]
TaNAC67 is a novel member of NAC family Sequence analysis showed TaNAC67 has high identity with reported stress responsive NAC members in the N-terminal DNA binding domains, including OsNAC1, TaGRAB1, TaNAC2, TaNAC2a, TaNAC4 and TaNAC69, while differs in the Cterminal transcriptional activation domain
Summary
Crop plants constantly encounter unfavorable environmental conditions, including drought, high salinity, and extreme temperatures, that significantly affect both biomass and grain yield worldwide. The NAC (NAM, ATAF, and CUC) superfamily is one of the largest plant-specific TF families. Proteins in this family are characterized by a highly conserved DNA binding NAC domain in the N-terminal and a highly diversified transcriptional activation domain in the C-terminal [10]. Considerable evidence showing that NACs play important roles in plant development, including pattern formation of embryos and flowers [14], secondary wall formation [15,16,17], leaf senescence [18,19,20], and root development [3,21]. NACs are involved in responses to various of biotic and abiotic stresses, including disease, drought, salt, cold and lowoxygen stresses, and act as targets of miRNAs [22]. It is believed that NAC TFs have potential to improve biotic and abiotic stress tolerances in plants [23,24,25], and some examples are listed below
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