State Key Laboratory for Conservation and Utilization of Subtropical Agro-bioresources/Guangdong Provincial Key Laboratory of Postharvest Science of Fruits and Vegetables/Engineering Research Center of Southern Horticultural Products Preservation, Ministry of Education, College of Horticulture, South China Agricultural University, Guangzhou, China.
Key Laboratory of Postharvest Biology of Subtropical Special Agricultural/Institute of Postharvest Technology of Agricultural Products, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China.
Plant Biotechnol J. 2024 Oct;22(10):2873-2886. doi: 10.1111/pbi.14410. Epub 2024 Jun 10.
Transcriptional regulation mechanisms underlying chilling injury (CI) development have been widely investigated in model plants and cold-sensitive fruits, such as banana (Musa acuminata). However, unlike the well-known NAC and WRKY transcription factors (TFs), the function and deciphering mechanism of heat shock factors (HSFs) involving in cold response are still fragmented. Here, we showed that hot water treatment (HWT) alleviated CI in harvested banana fruits accomplishing with reduced reactive oxygen species (ROS) accumulation and increased antioxidant enzyme activities. A cold-inducible but HWT-inhibited HSF, MaHsf24, was identified. Using DNA affinity purification sequencing (DAP-seq) combined with RNA-seq analyses, we found three heat shock protein (HSP) genes (MaHSP23.6, MaHSP70-1.1 and MaHSP70-1.2) and three antioxidant enzyme genes (MaAPX1, MaMDAR4 and MaGSTZ1) were the potential targets of MaHsf24. Subsequent electrophoretic mobility shift assay (EMSA), chromatin immunoprecipitation coupled with quantitative PCR (ChIP-qPCR) and dual-luciferase reporter (DLR) analyses demonstrated that MaHsf24 repressed the transcription of these six targets via directly binding to their promoters. Moreover, stably overexpressing MaHsf24 in tomatoes increased cold sensitivity by suppressing the expressions of HSPs and antioxidant enzyme genes, while HWT could recover cold tolerance, maintaining higher levels of HSPs and antioxidant enzyme genes, and activities of antioxidant enzymes. In contrast, transiently silencing MaHsf24 by virus-induced gene silencing (VIGS) in banana peels conferred cold resistance with the upregulation of MaHSPs and antioxidant enzyme genes. Collectively, our findings support the negative role of MaHsf24 in cold tolerance, and unravel a novel regulatory network controlling bananas CI occurrence, concerning MaHsf24-exerted inhibition of MaHSPs and antioxidant enzyme genes.
冷害（CI）发展的转录调控机制在模式植物和冷敏果实（如香蕉（Musa acuminata））中得到了广泛研究。然而，与著名的 NAC 和 WRKY 转录因子（TFs）不同，参与冷响应的热休克因子（HSFs）的功能和破译机制仍然不完整。在这里，我们表明热水处理（HWT）缓解了收获的香蕉果实中的 CI，同时减少了活性氧（ROS）的积累并增加了抗氧化酶的活性。鉴定出一个冷诱导但 HWT 抑制的 HSF，MaHsf24。使用 DNA 亲和纯化测序（DAP-seq）结合 RNA-seq 分析，我们发现三个热休克蛋白（HSP）基因（MaHSP23.6、MaHSP70-1.1 和 MaHSP70-1.2）和三个抗氧化酶基因（MaAPX1、MaMDAR4 和 MaGSTZ1）是 MaHsf24 的潜在靶标。随后的电泳迁移率变动分析（EMSA）、染色质免疫沉淀结合定量 PCR（ChIP-qPCR）和双荧光素酶报告（DLR）分析表明，MaHsf24 通过直接结合到它们的启动子上抑制这些六个靶标的转录。此外，在番茄中稳定过表达 MaHsf24 通过抑制 HSPs 和抗氧化酶基因的表达增加了对冷的敏感性，而 HWT 可以恢复对冷的耐受性，维持更高水平的 HSPs 和抗氧化酶基因以及抗氧化酶的活性。相比之下，通过病毒诱导的基因沉默（VIGS）在香蕉皮中瞬时沉默 MaHsf24 导致冷抗性，MaHSPs 和抗氧化酶基因的上调。总之，我们的研究结果支持 MaHsf24 在冷耐受性中的负调控作用，并揭示了一个新的调控网络，控制香蕉 CI 的发生，涉及 MaHsf24 对 MaHSPs 和抗氧化酶基因的抑制作用。
