神农香菊CibHLH1的鉴定及对光合特性的影响

Identification of CibHLH1 and its effect on photosynthetic characteristics in Chrysanthemum indicum var.aromaticum

bHLH家族是植物中第二大转录因子家族,对植物的生长发育、次生代谢和环境胁迫应答都起着重要的作用。本研究以神农香菊叶片cDNA为模板克隆了CibHLH1的全长序列,该基因全长738 bp,开放阅读框为630 bp。多序列比对分析及系统进化树结果表明,CibHLH1与菊花的CmbHLH1同源性最高。不同组织部位的荧光定量数据显示该基因在花中表达量最高,在根中表达量最低,亚细胞定位结果显示该基因定位在细胞核中。为进一步研究CibHLH1的功能,通过叶盘法将其转化烟草,发现过表达CibHLH1烟草叶片黄化,测定叶绿素含量发现,叶绿素a、叶绿素b及总叶绿素含量均显著降低。测定转基因烟草的光响应曲线及光合生理指标,结果表明过表达CibHLH1降低了烟草的最大净光合速率、表观量子效率、光饱和点和水分利用率,但其蒸腾速率、气孔导度和光补偿点均增加。综上所述,CibHLH1能够通过降低光合色素的含量而影响植物的光合能力。

The basic helix-loop-helix(bHLH)transcription factors are the second largest transcription factor family in plants and play an important role in plant growth and development,secondary metabolism and response to environmental stress.In this study,we cloned CibHLH1 using the leaf cDNA of Chrysanthemum indicum var.aromaticum as the template.The cloned gene has a 738 bp full-length sequence,and a 630 bp open reading frame.Multiple sequence comparison and phylogenetic investigation showed that CibHLH1 had the highest homology with CmbHLH1 of Chrysanthemum morifolium.The expression level of CibHLH1 was the highest in the flowers and lowest in roots.Subcellular localization revealed that the gene was located in the nucleus.CibHLH1 was transformed into tobacco(Nicotiana tabacum)by the leaf disk method to further study its functions.We found that the leaves of overexpressed tobacco became yellow and the contents of chlorophyll a,chlorophyll b and total chlorophyll were significantly reduced.The light response curve and photosynthetic physiological indexes of transgenic tobacco were evaluated,the results showed that overexpression of CibHLH1 decreased the maximum net photosynthetic rate,apparent quantum yield,light saturation point and water use efficiency,but increased the transpiration rate,stomatal conductance and light compensation point.In summary,CibHLH1 negatively affected the photosynthetic capacity of plants by reducing the content of photosynthetic pigments.