PuHSFA4a Enhances Tolerance To Excess Zinc by Regulating Reactive Oxygen Species Production and Root Development in Populus

Abstract

Zinc (Zn) is an essential micronutrient but in excess is highly toxic to plants. Plants regulate Zn homeostasis and withstand excess Zn through various pathways; these pathways are generally tightly regulated by a specific set of genes. However, the transcription factors involved in excess Zn tolerance have yet to be identified. Here, we characterized a Populus ussuriensis heat shock transcription factor A4a (PuHSFA4a) that acts as a positive regulator of excess Zn tolerance in P. ussuriensis. We used overexpression (PuHSFA4a-OE) and chimeric dominant repressor (PuHSFA4a-SRDX) lines to identify the targets of PuHSFA4a. PuHSFA4a transcription is specifically induced in roots by high Zn. Overexpression of PuHSFA4a conferred excess Zn tolerance and a dominant repressor version of PuHSFA4a increased excess Zn sensitivity in P. ussuriensis by regulating the antioxidant system in roots. PuHSFA4a coordinately activates genes related to abiotic stress responses and root development and directly binds to the promoter regions of glutathione-S-transferase U17 (PuGSTU17) and phospholipase A 2 (PuPLA 2). PuGSTU17 overexpression significantly increased GST activity and reduced reactive oxygen species levels in roots while PuGSTU17-RNA interference lines exhibited the opposite phenotype. Furthermore, PuPLA 2 overexpression promoted root growth under high Zn stress. Taken together, we provide evidence that PuHSFA4a coordinately activates the antioxidant system and root development-related genes and directly targets PuGSTU17 and PuPLA, thereby promoting excess Zn tolerance in P. ussuriensis roots.

SaHsfA4c From Sedum alfredii Hance Enhances Cadmium Tolerance by Regulating ROS-Scavenger Activities and Heat Shock Proteins Expression

“…Many studies have revealed crosstalk between Hsfs, ROS and ROS-scavenging enzymes. In Populus ussuriensis, PuHSFA4a can increase glutathione S-transferase activity to reduce ROS production and improve Zn resistance of roots by directly regulating the target gene PuGSTU17 (Zhang et al, 2019). Transgenic Arabidopsis overexpressing maize ZmHsf06 can enhance salt tolerance by increases POD and SOD activities (Li et al, 2015).…”

PtHSFA4a gene play critical roles in the adaptation of Arabidopsis thaliana plants to high-Zinc stress

“…In the current study, we identified a PtHSFA4a from P. trichocarpa which is an ortholog of PuHSFA4a in P. ussuriensis 8 . Seven nucleotides in the sequences of PtHSFA4a were different from PuHSFA4a.…”

“…These genes include: Populus alba AQUA1, 4 A. thaliana AtHMA4, 5 A. thaliana AtMTP1 6 and Oryza sativa OZT1 7 . In P. ussuriensis, the heat shock transcription factor (PuHSFA4a) appears to confer excess Zn tolerance 8 . However, up to now transcription factors that regulate the Zn detoxification seldom characterized in plants.…”

“…For example, overexpression of wheat TaHSFA4a in yeast conferred Cd tolerance 13 . We published a PuHSFA4a from Populus ussuriensis that targets PuGSTU17 and PuPLA 2 to promote excess Zn tolerance in P. ussuriensis roots directly 8 .…”

iTRAQ-Based Quantitative Proteomic Analysis of Heat Stress-Induced Mechanisms in Pepper Seedlings

“…To cope with heat stress, a set of defense mechanisms are activated to protect plants from the heat stressinduced damage, including the change of signal transduction and transcriptional regulation, the accumulation of osmolytes, the production of reactive oxygen species (ROS) scavenging enzymes, and the synthesis and accumulation of heat shock proteins (HSPs) [2,[5][6][7][8]. The generation and accumulation of ROS caused by heat stress can lead to the peroxidation of membrane lipids and proteins as well as carbohydrate oxidation and DNA damage [9,10]. To scavenge and detoxify ROS, plants have evolved both enzyme and non-enzyme systems [9].…”