State Key Laboratory of Tree Genetics and Breeding, National Engineering Research Center of Tree Breeding and Ecological Restoration, College of Biological Sciences and Technology, Beijing Forestry University, 85 Qinghua East Road, Beijing, 100083, China.
Department of Forest and Conservation Sciences, Faculty of Forestry, University of British Columbia, 2424 Main Mall, Vancouver, BC V6T 1Z4, Canada.
Tree Physiol. 2023 Nov 13;43(11):1964-1985. doi: 10.1093/treephys/tpad095.
Cold acclimation is a crucial biological process that enables conifers to overwinter safely. The late embryogenesis abundant (LEA) protein family plays a pivotal role in enhancing freezing tolerance during this process. Despite its importance, the identification, molecular functions and regulatory networks of the LEA protein family have not been extensively studied in conifers or gymnosperms. Pinus tabuliformis, a conifer with high ecological and economic values and with high-quality genome sequence, is an ideal candidate for such studies. Here, a total of 104 LEA genes were identified from P. tabuliformis, and we renamed them according to their subfamily group: PtLEA1-PtLEA92 (group LEA1-LEA6), PtSMP1-PtSMP6 (group seed maturation protein) and PtDHN1-PtDHN6 (group Dehydrin). While the sequence structure of P. tabuliformis LEA genes are conserved, their physicochemical properties exhibit unique characteristics within different subfamily groupings. Notably, the abundance of low-temperature responsive elements in PtLEA genes was observed. Using annual rhythm and temperature gradient transcriptome data, PtLEA22 was identified as a key gene that responds to low-temperature induction while conforming to the annual cycle of cold acclimation. Overexpression of PtLEA22 enhanced Arabidopsis freezing tolerance. Furthermore, several transcription factors potentially co-expressed with PtLEA22 were validated using yeast one-hybrid and dual-luciferase assays, revealing that PtDREB1 could directly bind PtLEA22 promoter to positively regulate its expression. These findings reveal the genome-wide characterization of P. tabuliformis LEA genes and their importance in the cold acclimation, while providing a theoretical basis for studying the molecular mechanisms of cold acclimation in conifers.
冷驯化是一种关键的生物过程，使针叶树能够安全越冬。晚期胚胎丰富（LEA）蛋白家族在提高其在这个过程中的抗冻性方面起着关键作用。尽管其重要性，但在针叶树或裸子植物中，LEA 蛋白家族的鉴定、分子功能和调控网络尚未得到广泛研究。具有高生态和经济价值以及高质量基因组序列的白皮松是进行此类研究的理想候选者。在这里，从白皮松中总共鉴定了 104 个 LEA 基因，我们根据它们的亚家族分组重新命名为：PtLEA1-PtLEA92（LEA1-LEA6 组）、PtSMP1-PtSMP6（种子成熟蛋白组）和 PtDHN1-PtDHN6（脱水素组）。虽然白皮松 LEA 基因的序列结构是保守的，但它们的物理化学性质在不同的亚家族分组中表现出独特的特征。值得注意的是，观察到 PtLEA 基因中低温响应元件的丰富度。使用年度节律和温度梯度转录组数据，鉴定出 PtLEA22 是对低温诱导响应的关键基因，同时符合冷驯化的年度周期。PtLEA22 的过表达增强了拟南芥的抗冻性。此外，使用酵母单杂交和双荧光素酶测定验证了几种可能与 PtLEA22 共表达的转录因子，表明 PtDREB1 可以直接结合 PtLEA22 启动子，正向调节其表达。这些发现揭示了白皮松 LEA 基因的全基因组特征及其在冷驯化中的重要性，同时为研究针叶树冷驯化的分子机制提供了理论基础。
