Gill Arshdeep Singh, Wolyn David J
Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada.
Front Plant Sci. 2024 Aug 16;15:1442784. doi: 10.3389/fpls.2024.1442784. eCollection 2024.
Asparagus ( L. is an important vegetable crop in southern Ontario, Canada, where winter air and soil temperatures below 0°C are common. Consequently, cultivars growing in this area must possess winterhardiness and freezing tolerance for survival. Asparagus acquires freezing tolerance in the fall through cold acclimation and loses freezing tolerance in the spring through deacclimation. To understand the molecular bases of these processes, transcriptomic analysis (RNA-Seq) was conducted on two cultivars, one adapted, 'Guelph Millennium' (GM), and one unadapted, 'UC157' (UC), to the winter conditions of southern Ontario. RNA extracted from bud and rhizome tissues, sampled on three dates during early spring and late fall, was subjected to sequencing. In the fall, the numbers of differentially expressed (DE) genes at the second and third harvests increased, relative to the first harvest, in dormant buds and rhizomes as freezing tolerance of cultivars increased, and the majority of DE genes were downregulated. In spring, freezing tolerance decreased as plants deacclimated and most genes DE at second and third harvests were upregulated in both cultivars. GM had lower LT (lethal temperature at which 50% of plants die) values and hence higher freezing tolerance than UC on specific sampling dates during both spring and fall, and expression patterns of specific genes were correlated with LT differences. Functional analysis revealed that these genes were involved in carbohydrate metabolic process, plant hormone signal transduction (auxin and gibberellin), proline metabolism, biosynthesis of secondary metabolites, circadian rhythm, and late embryogenesis abundant proteins and could be associated with cold acclimation and deacclimation processes. These findings will help researchers understand the molecular mechanisms of freezing tolerance in asparagus, leading to breeding and genetic strategies to improve the trait.
芦笋（L.）是加拿大安大略省南部一种重要的蔬菜作物，该地区冬季空气和土壤温度低于0°C很常见。因此，在该地区种植的品种必须具备抗寒性和耐冻性才能存活。芦笋在秋季通过低温驯化获得耐冻性，在春季通过脱驯化失去耐冻性。为了了解这些过程的分子基础，对两个品种进行了转录组分析（RNA测序），一个适应安大略省南部冬季条件的品种“圭尔夫千禧”（GM），另一个不适应的品种“UC157”（UC）。从早春和晚秋三个日期采集的芽和根茎组织中提取的RNA进行了测序。在秋季，随着品种耐冻性的提高，休眠芽和根茎中第二次和第三次收获时差异表达（DE）基因的数量相对于第一次收获有所增加，且大多数DE基因被下调。在春季，随着植物脱驯化，耐冻性降低，两个品种在第二次和第三次收获时大多数DE基因均被上调。在春季和秋季的特定采样日期，GM的致死温度（50%植株死亡时的温度）值较低，因此比UC具有更高的耐冻性，特定基因的表达模式与致死温度差异相关。功能分析表明，这些基因参与碳水化合物代谢过程、植物激素信号转导（生长素和赤霉素）、脯氨酸代谢、次生代谢物生物合成、昼夜节律以及晚期胚胎发生丰富蛋白，可能与低温驯化和脱驯化过程有关。这些发现将有助于研究人员了解芦笋耐冻性的分子机制，从而制定改良该性状的育种和遗传策略。
