Low temperature is one of the key environmental stresses that impair plant growth and significantly restricts the productivity and spatial distribution of crop plants. Gossypium thurberi, a wild diploid cotton species, has adapted to a wide range of temperatures and exhibits a better tolerance to chilling stress. Here, we compared phenotypes and physiochemical changes in G. thurberi under cold stress and found this species indeed showed better cold tolerance. Therefore, to understand the molecular mechanisms of the cold tolerance in G. thurberi, we compared transcription changes in leaves of G. thurberi under cold stress by high-throughput transcriptome sequencing. In total, 35 617 unigenes were identified in the whole-genome transcription profile, and 4226 differentially expressed genes (DEGs) were discovered in the leaves upon cold treatment. Gene Ontology (GO) classification analyses showed that the majority of DEGs belonged to categories of signal transduction, transcription factors (TFs) and carbohydrate transport and metabolism. The expression of several cold-responsive genes such as ICE1, CBF4, RAP2-7 and abscisic acid (ABA) biosynthesis genes involved in different signalling pathways were induced after G. thurberi seedlings were exposed to cold stress. Furthermore, cold sensitivity was increased in CBF4 and ICE2 virus-induced gene silencing (VIGS) plants, and high level of malondialdehyde (MDA) showed that the CBF4 and ICE2 silenced plants were under oxidative stress compared to their wild types, which relatively had higher levels of antioxidant enzyme activity, as evident by high levels of proline and superoxide dismutase (SOD) content. In conclusion, our findings reveal a new regulatory network of cold stress response in G. thurberi and broaden our understanding of the cold tolerance mechanism in cotton, which might accelerate functional genomics studies and genetic improvement for cold stress tolerance in cultivated cotton.

中文翻译：

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比较转录组、生理生化分析揭示了 CBF4 和 ICE2 介导的增强苏氏棉冷应激耐受性的反应机制。

低温是损害植物生长并严重限制作物生产力和空间分布的关键环境胁迫之一。苏氏棉 (Gossypium thurberi) 是一种野生二倍体棉种，能够适应较宽的温度范围，并且对寒冷胁迫表现出更好的耐受性。在这里，我们比较了冷胁迫下的G. thurberi的表型和理化变化，发现该物种确实表现出更好的耐冷性。因此，为了了解G. thurberi耐冷的分子机制，我们通过高通量转录组测序比较了冷胁迫下G. thurberi叶片的转录变化。在全基因组转录谱中总共鉴定了 35 617 个 unigene，并在冷处理后的叶子中发现了 4226 个差异表达基因（DEG）。基因本体（GO）分类分析表明，大多数DEG属于信号转导、转录因子（TF）和碳水化合物转运和代谢类别。瑟伯里幼苗暴露于冷胁迫后，诱导了参与不同信号通路的多个冷响应基因（如ICE1、CBF4、RAP2-7和脱落酸（ABA）生物合成基因）的表达。此外，CBF4和ICE2病毒诱导的基因沉默（VIGS）植物的冷敏感性增加，并且高水平的丙二醛（MDA）表明CBF4和ICE2沉默的植物与野生型相比处于氧化应激下，相对具有更高的氧化应激水平。抗氧化酶活性水平，从脯氨酸和超氧化物歧化酶 (SOD) 含量高即可看出。总之，我们的研究结果揭示了苏氏棉冷胁迫反应的新调控网络，拓宽了我们对棉花耐冷机制的理解，这可能会加速栽培棉花的功能基因组学研究和耐冷胁迫遗传改良。