Transgenic poplar with the Zygophyllum xanthoxylon zinc finger protein transcription factor ZxZF gene shows improved drought resistance by regulating hormone signal

Abstract

Drought stress has emerged as a primary factor constraining the growth, development, and yield of plants. The synthesis and signal transduction pathways of plant hormones play key roles in physiological adaptation to drought stress. The drought-resistance-associated C2H2 zinc finger protein transcription factor gene (ZxZF), which we previously identified, was transformed into Bofeng No. 1 poplar (Populus × euramericana c1. ‘Bofeng1’). This study evaluated the mechanism of drought resistance improvement from the perspective of gene interaction networks between transcription factors and genes that regulate plant hormone signals. Transcriptome analysis shows that many differentially expressed genes (DEGs) between before and after drought and between wild-type (WT) and ZxZF-overexpression (OE) lines was significantly enriched in plant hormone signal transduction pathways in the KEGG pathway. Quantitative analysis of hormone content and expression of genes related to synthesis and signal transduction showed that abscisic acid (ABA) content and proline content in OE lines increased significantly after drought stress, which could not only enhance water retention ability of plants, but also avoid excessive amplification of ABA signals. Drought stress also increases the jasmonic acid (JA) content in OE lines, and JA can increase the content of antioxidant enzymes in OE lines through downstream signal transduction pathways, thus further eliminating ROS in plant leaves. In addition, as growth hormones, IAA and GA could be associated with ABA and JA through various downstream signal transduction pathways, and the interaction between hormones and hormone signal transduction pathways could jointly improve the drought resistance of ZxZF-OE lines.