Scientists Find Transcription Factor MdWRKY9 Boosts Apple's Salt Tolerance

Salt stress poses a significant threat to global agricultural productivity, impacting over 6% of the world's land and challenging crop cultivation. Apple trees are vulnerable to high salt concentrations, which hinder their growth and degrade fruit quality. To address this challenge, researchers looked at the hormonal and genetic pathways that govern how apples respond to saline environments.

A new study published in Horticulture Research by researchers from Shandong Agricultural University has identified that the transcription factor MdWRKY9 is a key player in boosting apple's resilience. The study reveals that MdWRKY9 interacts with the jasmonic acid (JA) signaling pathway, a plant hormone known to enhance salt tolerance, to regulate genes essential for ion homeostasis. Under salt stress, the expression of MdWRKY9 significantly increases in apple roots. Experiments with transgenic apples overexpressing this factor showed markedly enhanced salt tolerance, with improved growth maintained even in high-salt conditions.

The mechanism involves MdWRKY9 directly binding to the promoters of genes crucial for ionic balance, specifically MdNHX1 and MdSOS2, thereby boosting their expression. Furthermore, the JA signaling pathway modulates this process by triggering the degradation of JAZ proteins, which normally repress the pathway. This degradation frees MdWRKY9 to activate its target genes, thereby maintaining cellular ion homeostasis, which is necessary for survival during salt stress. These findings provide a significant molecular understanding, paving the way for the development of genetically modified apple varieties—and potentially other crops—with enhanced salt tolerance to secure global food production in increasingly saline-prone agricultural regions.

For more details, read this article or download the open-access paper in Horticulture Research.