A natural 294-bp indel in the VviHKT1;1 proximal promoter influences the salt resistance of VviHKT1;1-overexpressing Arabidopsis
摘要
VviHKT1;1, a member of the high-affinity K+ transporter (HKT) family, is a major quantitative trait locus responsible for limitation of Na+ accumulation in grape leaves. However, the regulatory mechanism of VviHKT1;1 remains largely unexplored. In this study, VviHKT1;1 transcript profile was analyzed under salt stress conditions, revealing distinct expression patterns among different cultivars. Furthermore, the promoter region of VviHKT1;1 was isolated from grape varieties with differential salt tolerance and a natural 294-bp InDel (insertion/deletion) in the VviHKT1;1 proximal promoter, named pVviHKT1;1In and pVviHKT1;1Del was found. Compared to pVviHKT1;1Del::GUS, pVviHKT1;1In::GUS exhibited stronger activity of GUS in the above-ground tissues of transgenic Arabidopsis thaliana under both normal and salt stress conditions. Overexpression of VviHKT1;1 driven by either pVviHKT1;1In or pVviHKT1;1Del in A. thaliana significantly enhanced the salt resistance by reducing Na+ content in roots and shoots. Furtherly, the VviHKT1;1 promoter containing the 294-bp insertion demonstrated a significant upregulation of VviHKT1;1 transcription level in stems of VviHKT1;1-overexpressing A. thaliana compared to the 294-bp deletion under both control and salt stress conditions. This facilitated the distribution of a greater amount of Na+ into the stems, thereby more effectively limiting the sodium flux to the flowers. As the result, transgenic Arabidopsis plants with pVviHKT1;1In::VviHKT1;1 exhibited better growth, accompanied by significantly increased stem height and number of seed pods compared to the transgenic lines of pVviHKT1;1Del::VviHKT1;1. Collectively, the natural 294-bp InDel in VviHKT1;1 promoter might modulate the Na+ distribution in above-ground tissues, thereby influencing plant salt tolerance.