A functional study of the role of SgNAC1 in salt tolerance in Stylosanthes

doi:10.11686/cyxb2025436

Abstract

Abstract:

Stylosanthes （stylo） is an economically important leguminous forage crop in tropical and subtropical regions. It plays critical roles in forage production， soil and water conservation， and orchard ground cover. Because its role is similar to that of alfalfa （Medicago sativa）， stylo is often referred to as ‘tropical alfalfa’. With the continuing global expansion of saline-alkali land areas， salt stress reduces the growth and yield of stylo， and has become a key constraint on its cultivation and promotion. Therefore， it is urgent to identify key genes related to salt tolerance and clarify their functions. The NAC family of transcription factors is known to regulate salt tolerance， but the specific role of SgNAC1 in the salt tolerance of stylo remains unclear. In this study， we analyzed the transcript profiles of SgNAC1 in leaves and stems of the Stylosanthesguianensis line ‘YN02’ using quantitative real-time PCR. The results show that under salt stress （150 mmol·L^-1NaCl）， the transcript abundance of SgNAC1 in leaves decreased to the lowest level at 2 hours after treatment （HAT）， but peaked in stems at 6 HAT. After treatment with abscisic acid （ABA）， the transcript abundance of SgNAC1 in both leaves and stems peaked at 1 HAT. In the combined ABA+NaCl treatment， the transcript abundance of SgNAC1 in leaves peaked at 0.5 HAT， whereas in stems， it exhibited two peaks at 1 HAT and 12 HAT. Thus， SgNAC1 in stems responded to salt stress at approximately 12 HAT， and to both ABA and ABA+NaCl at approximately 1 HAT. Under salt stress， the transcript abundance of SgNAC1 in leaves decreased significantly at 2 HAT， implying that it may be regulated by other factors. The dual expression peaks of SgNAC1 in stems after treatment with ABA+NaCl may indicate a synergistic effect of NaCl and ABA. Transgenic tobacco （Nicotiana tabacum） lines overexpressing SgNAC1 （SgNAC1-OE） were obtained by transforming wild-type tobacco via the Agrobacterium tumefaciens-mediated leaf disc method. When both wild-type and SgNAC1-OE tobacco plants were subjected to salt stress （300 mmol·L^-1NaCl）， the SgNAC1-OE tobacco plants showed significantly increased proline levels and salt tolerance， compared with the wild-type plants. The results of this study reveal the transcript profiles of SgNAC1 in different tissues of stylo， and the experiments with transgenic tobacco lines overexpressing SgNAC1 confirm its ability to increase salt tolerance. Together， our results provide a theoretical basis for further research on salt tolerance mechanisms， and identify a genetic resource for breeding salt-tolerant stylo.

Key words: Stylosanthes, SgNAC1 gene, transgenic tobacco, gene expression, salt tolerance

Yi-hua WANG, Ci REN, Pan-yu ZHANG, Cui-ling LIU, Liang-liang HE, Jie-yi LI, Chao LIU, Shu CHEN. A functional study of the role of SgNAC1 in salt tolerance in Stylosanthes[J]. Acta Prataculturae Sinica, 2026, 35(10): 144-155.

Figures/Tables 7

Table 1 Primers used in this study

引物名称Name of the primer	正向引物序列Forward primer sequence （5'→3'）	反向引物序列Reverse primer sequence （5'→3'）
SgNAC1	TCTAGAATGGCAGCTGAACTTCAATTGC	GGATCCTCAGAACGGTTTCTGCAGGTTC
SgNAC1-qPCR	TTCCGATCATAGCCGAAATC	TGCCTTCCAGTACCCAGTTC
SgActin-qPCR	TCGATTGGATCTTGCAGGGC	TGGACAACGGAATCTCTCAGC

Fig.1 Analysis of cis-acting elements in the promoter of SgNAC1 gene and its gene structure

Fig.2 Changes in the relative expression levels of the SgNAC1 gene in leaves and stems of Stylosanthes ‘YN02’ under different treatments

Fig.3 Identification of Basta resistance in SgNAC1-OE transgenic tobacco， PCR identification and qRT-PCR analysis of the SgNAC1 gene

Fig.4 Differences in the length-to-width ratio and flower color between genetically modified and wild N. tabacum leaves

Fig.5 Phenotypic changes in tobacco under salt stress

Fig.6 Changes in physiological indicators of wild-type and SgNAC1-overexpressing tobacco under salt stress

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