Functional Analysis of Haloxylon Ammodendron Heat Shock Factor HaHsfA5 in Heat Stress Memory

Objective Previous study has found that the heat shock factor gene HaHsfA5 in Haloxylon ammodendron exhibits expression characteristics of heat stress memory. This study investigates the function of HaHsfA5 in heat stress memory.

Methods Using the method of transient expression in tobacco epidermal cells to analyze the subcellular localization of HaHsfA5. Using homozygous lines of HaHsfA5 transgenic Arabidopsis and the wild-type Arabidopsis (WT) as materials. The germination rates, the germination potential, and the green seedling rates of the seeds were statistically analyzed after the heat stress pretreatment. Futhetmore, the growth phenotype, survival rates, cell mortality rates, chlorophyll and proline contents, activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and fluorescence quantitative PCR (qRT-PCR) of genes related to the above physiological indices of the seedlings were statistically analyzed after the heat stress training (37 ℃ 90 min) and the second heat stress (47 ℃ 1 h) treatment.

Results Subcellular localization results show that HaHsfA5 is located in the nucleus. The study on HaHsfA5 overexpressing lines showed that overexpression of HaHsfA5 promoted the germination of transgenic Arabidopsis seeds under normal growth and heat stress conditions; furthermore, after the heat stress training (37 ℃ 90 min) and the second heat stress (47 ℃ 1h) treatment, the HaHsfA5 overexpressing lines had higher survival rates and lower cell death rates compared to WT. The antioxidant enzymes activities, and chlorophyll content of HaHsfA5 overexpressing lines were higher than those of WT after the heat stress training. qRT-PCR analysis showed that the expression levels of genes related to antioxidant pathways in HaHsfA5 overexpressing lines were higher than those in WT after the second heat stress.

Conclusion Overexpression of HaHsfA5 prompted the tolerance of transgenic Arabidopsis to the second heat stress, indicating HaHsfA5 is an important regulatory factor in heat stress memory.