Abstract
GhNAC18 is a novel NAC gene that was isolated from cotton (Gossypium hirsutum L.). The full-length cDNA was 1511 bp including an open reading frame of 1260 bp in length and encodes a protein of 419 amino acids. With qRT-PCR analysis, GhNAC18 was downregulated during natural and dark-induced senescence, implicating this gene as anti-aging gene in cotton. Analysis of its promoter revealed a group of putative cis-acting elements especially, the light and stress responsive elements, indicating that it may have a potential role in leaf development. Additionally, GhNAC18 was found to have transcriptional activation activities on its C-terminal region and by bioinformatics analysis, GhNAC18 was localized in the nucleus. Tissue specific expression analysis indicated that GhNAC18 is constitutively expressed in roots, stems, earlier stages of senescing leaves, fibers and flower parts with high expression levels registered in the young leaves and cotyledon leaves. GhNAC18 was up-regulated by exogenous application of various phytohormones including salicylic acid (SA), methyl Jasmonate (MeJA) and ethylene (ET) but downregulated with abscisic acid (ABA). Moreover, the gene was induced by drought (PEG6000), H2O2, cold (4°C) and wounding but was inhibited by high salinity. These results indicated that GhNAC18 is a transcriptional activator that is involved in leaf development, especially inhibition of leaf senescence and plant stress responses in cotton. This study provides fundamental information on understanding the function of GhNAC18 gene in cotton leaf senescence and stress tolerance and thereafter its manipulation for breeding of late-aging and stress-tolerant cultivars. Key words: GhNAC18, stress response, senescence, Gossypium hirsutum L. NAC.
Highlights
Plants face survival challenges posed by ever varying adverse environmental conditions which include but not limited to abiotic stress such as cold, high salinity, drought and extreme temperatures (Fujita et al, 2004; Ning et al, 2010; Nakashima et al, 2011)
These results indicated that GhNAC18 is a transcriptional activator that is involved in leaf development, especially inhibition of leaf senescence and plant stress responses in cotton
To date numerous NAC family genes have been isolated and characterized revealing a wide range of functions they play in plant species
Summary
Plants face survival challenges posed by ever varying adverse environmental conditions which include but not limited to abiotic stress such as cold, high salinity, drought and extreme temperatures (Fujita et al, 2004; Ning et al, 2010; Nakashima et al, 2011) Biotic attacks such as infectious pathogens complicate the sessile habit of plants. In this regard, plants adapt to these dynamic conditions by evoking responses at physiological, biochemical and molecular levels (Nakashima et al, 2011; Fan et al, 2015) including regulation of genes enhancing survivability (Nuruzzaman et al, 2013).
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