Overexpression of the GmNAC2 Gene, an NAC Transcription Factor, Reduces Abiotic Stress Tolerance in Tobacco

Abstract Background: Pearl millet (Pennisetum glaucum) is a cereal crop that possesses the ability to withstand drought, salinity and high temperature stresses. The NAC [NAM (No Apical Meristem), ATAF1 and (Arabidopsis thaliana Activation Factor 1), and CUC2 (Cup-shaped Cotyledon)] transcription factor family is one of the largest transcription factor families in plants. NAC family members are known to regulate plant growth and abiotic stress tolerance. Currently, no reports are available on the functions of the NAC family in pearl millet. Results: Our genome-wide analysis found 151 NAC transcription factor genes (PgNACs) in the pearl millet genome. Phylogenetic analysis divided these NAC transcription factors into 11 groups (A-K). Three PgNACs (-073, -29, and -151) were found to be membrane-associated transcription factors (MTF). Seventeen other conserved motifs were found in PgNACs. Based on the similarity of PgNACs to NAC proteins in other species, the functions of PgNACs were predicted. In total, 88 microRNA target sites were predicted in 59 PgNACs. A previously performed transcriptome analysis suggests that the expression of 30 and 42 PgNACs are affected by salinity stress and drought stress, respectively. The expression of 36 randomly selected PgNACs was examined by quantitative reverse transcription-PCR. Many of these genes showed diverse salt- and drought-responsive expression patterns in roots and leaves. These results confirm that PgNACs are potentially involved in regulating abiotic stress tolerance in pearl millet.Conclusion: The pearl millet genome contains 151 NAC transcription factor genes that can be classified into 11 groups. Many of these genes are either upregulated or downregulated by either salinity or drought stress and may therefore contribute to establishing stress tolerance in pearl millet.

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Structure-function relationship of Gossypium hirsutum NAC transcription factor, GhNAC4 with regard to ABA and abiotic stress responses

10.1101/2020.05.28.121665 ◽

2020 ◽

Author(s):

Vikas Shalibhadra Trishla ◽

Pulugurtha Bharadwaja Kirti

Keyword(s):

Transcription Factor ◽

Abiotic Stress ◽

Stress Tolerance ◽

Abiotic Stress Tolerance ◽

Nac Transcription Factor ◽

Wild Type ◽

Nac Domain ◽

Transcriptional Regulatory ◽

Function Relationship ◽

Relationship Of

AbstractOur previous study demonstrated that the expression of GhNAC4, a NAC transcription factor from cotton, was induced by abiotic stresses and abscisic acid (ABA) treatment. In the present study, we investigated the molecular mechanisms underlying ABA and stress response of GhNAC4. Over-expression of GhNAC4 in transgenic tobacco conferred tolerance to salinity and drought treatments with associated enhanced expression of several stress-responsive marker genes. GhNAC4 is a nuclear protein that exhibits transcriptional activation property, and the C-terminal transcriptional regulatory (TR) domain is responsible for it. GhNAC4 also forms homo-dimers and the N-terminal NAC-domain is essential for this activity. The structure-function relationship of NAC transcription factors, particularly with respect to abiotic stress tolerance remains largely unclear. In this study, we investigated the domains essential for the biochemical functions of GhNAC4. We developed transgenic tobacco plants overexpressing the GhNAC4 NAC-domain and the TR-domain separately. NAC-domain transgenics showed hypersensitivity to exogenous ABA while TR-domain transgenics exhibited reduced sensitivity. Abiotic stress assays indicated that transgenic plants expressing both the domains separately were more tolerant than wild-type plants with the NAC-domain transgenics showing increased tolerance as compared to TR-domain transgenics. Expression analysis revealed that various stress-responsive genes were upregulated in both NAC-domain and TR-domain transgenics as compared to wild-type under salinity and drought treatments. These results suggest that the stress tolerance ability of GhNAC4 is associated with both the component domains while the ABA responsiveness is largely associated with N-terminal NAC-domain.Key MessageNAC and transcriptional regulatory domains are responsible for the abiotic stress tolerance ability of the cotton NAC transcription factor GhNAC4 while the ABA-responsiveness is largely associated with the NAC-domain.

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