Abstract
BackgroundNAC proteins (NAM (No apical meristem), ATAF (Arabidopsis transcription activation factor) and CUC (cup-shaped cotyledon)) are plant-specific transcription factors reported to be involved in regulating growth, development and stress responses. Salinity responsive transcriptome profiling in a set of contrasting finger millet genotypes through RNA-sequencing resulted in the identification of a NAC homolog (EcNAC 67) exhibiting differential salinity responsive expression pattern.MethodsFull length cDNA of EcNAC67 was isolated, characterized and validated for its role in abiotic stress tolerance through agrobacterium mediated genetic transformation in a rice cultivar ASD16.ResultsBioinformatics analysis of putative NAC transcription factor (TF) isolated from a salinity tolerant finger millet showed its genetic relatedness to NAC67 family TFs in related cereals. Putative transgenic lines of rice over-expressing EcNAC67 were generated through Agrobacterium mediated transformation and presence/integration of transgene was confirmed through PCR and southern hybridization analysis. Transgenic rice plants harboring EcNAC67 showed enhanced tolerance against drought and salinity under greenhouse conditions. Transgenic rice plants were found to possess higher root and shoot biomass during stress and showed better revival ability upon relief from salinity stress. Upon drought stress, transgenic lines were found to maintain higher relative water content and lesser reduction in grain yield when compared to non-transgenic ASD16 plants. Drought induced spikelet sterility was found to be much lower in the transgenic lines than the non-transgenic ASD16.ConclusionResults revealed the significant role of EcNAC67 in modulating responses against dehydration stress in rice. No detectable abnormalities in the phenotypic traits were observed in the transgenic plants under normal growth conditions. Results indicate that EcNAC67 can be used as a novel source for engineering tolerance against drought and salinity stress in rice and other crop plants.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-016-0261-1) contains supplementary material, which is available to authorized users.
Highlights
NAC proteins (NAM (No apical meristem), ATAF (Arabidopsis transcription activation factor) and CUC) are plant-specific transcription factors reported to be involved in regulating growth, development and stress responses
Genetic material and stress treatments Based on the results of our earlier study [42], a putative candidate gene namely a NAC transcription factor 67 (EcNAC67) exhibiting contrasting salinity response between susceptible (CO 12) and tolerant (Trichy 1) finger millet genotypes was selected for functional validation
Validation of differential regulation of EcNAC67 during salinity stress qRT-PCR analysis of salinity responsive expression pattern in control and salinity stressed leaves, shoots and roots of Trichy 1 revealed that, EcNAC67 transcript was found to be abundant in leaves, followed by roots and minimum in shoots (Fig. 1)
Summary
NAC proteins (NAM (No apical meristem), ATAF (Arabidopsis transcription activation factor) and CUC (cup-shaped cotyledon)) are plant-specific transcription factors reported to be involved in regulating growth, development and stress responses. Drought and salinity remain at the top in affecting productivity of major food grains such as rice, wheat, maize etc., and predicted climate change may cause serious salinization of more than 50 % of arable lands by 2050 [1] This necessitates genetic manipulation of tolerance against these two major abiotic stresses in major food crops which remains very difficult through conventional breeding methods due to complexity of tolerance mechanisms [2, 3]. Genetic engineering strategies for improving salinity tolerance in crop plants includes manipulation of various metabolic pathways viz., accumulation of osmolytes, antioxidant enzymes, regulating the uptake/compartmentalization of salts, transcriptional factors and various signalling pathway components etc., [7] In this context, identification and validation of novel genes associated with various component traits controlling salinity tolerance in candidate crops/organisms is an important step which will allow us to manipulate salinity tolerance in any agriculturally important crop
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