Primers for qRT-PCR reaction.

Small molecular heat shock proteins (sHSPs) belong to the HSP family of molecular chaperones. Under high-temperature stress, they can prevent the aggregation of irreversible proteins and maintain the folding of denatured proteins to enhance heat resistance. In this study, the CmHSP17.9-1 and CmHSP17.9-2 genes, which were cloned from chrysanthemum (Chrysanthemum×morifolium ‘Jinba’) by homologous cloning, had a complete open reading frame of 480 bp each, encoding 159 amino acids. The protein subcellular localization analysis showed that CmHSP17.9-1 and CmHSP17.9-2 were located in the cytoplasm and mostly aggregated in granules, especially around the nucleus. Real-time quantitative PCR (qRT-PCR) analysis showed that the relative expression level of the CmHSP17.9-1 and CmHSP17.9-2 genes was highest in the terminal buds of the chrysanthemum, followed by the leaves. CmHSP17.9-1 and CmHSP17.9-2 overex-pression vectors were constructed and used to transform the chrysanthemum; overexpression of these genes led to the chrysanthemum phenotypes being less affected by high-temperature, and the antioxidant capacity was enhanced. The results showed that chrysanthemum with overex-pression of the CmHSP17.9-1 and CmHSP17.9-2 genes had stronger tolerance than the wild type chrysanthemum after high-temperature treatment or some degree of heat exercise, and overex-pression of the CmHSP17.9-1 gene led to stronger heat resistance than that of the CmHSP17.9-2 gene, providing an important theoretical basis for the subsequent molecular breeding and pro-duction applications of chrysanthemum.

小分子热激蛋白（small molecular heat shock proteins，sHSPs）隶属于热激蛋白（Heat Shock Protein，HSP）家族，属于分子伴侣类蛋白。在高温胁迫条件下，此类蛋白可阻断不可逆蛋白的聚集过程，并维持变性蛋白的折叠状态，以此增强耐热性。本研究通过同源克隆技术，从菊花（Chrysanthemum×morifolium ‘Jinba’）中克隆得到CmHSP17.9-1与CmHSP17.9-2两个基因；二者均含有长度为480 bp的完整开放阅读框（open reading frame，ORF），编码159个氨基酸残基。蛋白亚细胞定位（subcellular localization）分析结果显示，CmHSP17.9-1与CmHSP17.9-2蛋白定位于细胞质中，且多以颗粒状聚集，尤其富集于细胞核周边。实时荧光定量聚合酶链反应（real-time quantitative PCR，qRT-PCR）分析结果表明，CmHSP17.9-1与CmHSP17.9-2基因在菊花顶芽中的相对表达量最高，其次为叶片。本研究构建了CmHSP17.9-1与CmHSP17.9-2的过表达（overexpression）载体，并将其转化菊花；结果显示，过表达这两个基因可使菊花表型受高温胁迫的影响程度降低，同时提升其抗氧化能力。研究结果表明，经高温处理或一定程度热锻炼后，过表达CmHSP17.9-1与CmHSP17.9-2基因的转基因菊花较野生型菊花具有更强的耐受性；且过表达CmHSP17.9-1基因的菊花耐热性强于过表达CmHSP17.9-2基因的植株。本研究结果为后续菊花的分子育种及生产应用提供了重要的理论依据。