茶树CsCCD基因家族全基因组鉴定及乌龙茶LED补光晾青下表达分析

Genome-wide identification of CsCCD gene family in tea plant (Camellia sinensis) and expression analysis of the oolong tea processing with supplementary LED light

摘要:

类胡萝卜素裂解双加氧酶(carotenoid cleavage dioxygenase, CCD) 家族成员能催化类胡萝卜素裂解生成挥发性芳香物质并参与植物激素的合成。为探究茶树CsCCD基因家族成员生物学功能及基因表达模式，采用生物信息学手段进行了茶树全基因组CsCCD基因家族成员的鉴定，预测分析了其基因结构、保守基序、染色体定位、蛋白的理化性质、进化特性、互作网络、启动子顺式作用元件，并通过RT-qPCR测定了茶树不同叶位、乌龙茶加工过程中光照处理下CsCCD的相对表达量。共鉴定出11个茶树CsCCD基因家族成员，含有1–11个外显子、0–10个内含子不等；平均氨基酸个数为519 aa，平均分子质量为57 643.35 Da；聚类分析显示，CCD1、CCD4、CCD7、CCD8和NCED5个亚族各自聚成一类。茶树CsCCD基因家族主要含有胁迫响应元件、激素响应元件、光响应元件与多因素响应元件，且以光响应元件最多(142个)。进一步对茶树CsCCD基因在茶树不同叶位及乌龙茶加工过程中LED补光晾青过程的表达模式分析发现，CsCCD1、CsCCD4在成熟叶中表达量高于嫩叶及嫩茎，且随做青次数的增加，表达量呈下降趋势，但LED补光可在做青前期显著促进其基因表达；NCED亚家族成员整体呈现嫩叶表达量高于成熟叶及嫩茎趋势，但在做青过程中表达趋势不一，NCED3的表达水平先升后降，最高可达鲜叶的15倍以上，且在做青后期LED补光可极显著促进其基因表达。茶树CsCCD基因家族成员表达情况受机械力及光照调控，可进一步为优化茶叶加工工艺并提升茶叶品质奠定基础。

Abstract:

Carotenoid cleavage dioxygenase (CCD) family is important for production of volatile aromatic compounds and synthesis of plant hormones. To explore the biological functions and gene expression patterns of CsCCD gene family in tea plant, genome-wide identification of CsCCD gene family was performed. The gene structures, conserved motifs, chromosome locations, protein physicochemical properties, evolutionary characteristics, interaction network and cis-acting regulatory elements were predicted and analyzed. Real time-quantitative reverse transcription PCR (RT-qPCR) was used to detect the relative expression level of CsCCD gene family members under different leaf positions and light treatments during processing. A total of 11 CsCCD gene family members, each containing exons ranging from 1 to 11 and introns ranging from 0 to 10, were identified. The average number of amino acids and molecular weight were 519 aa and 57 643.35 Da, respectively. Phylogenetic analysis showed the CsCCD gene family was clustered into 5 major groups (CCD1, CCD4, CCD7, CCD8 and NCED). The CsCCD gene family mainly contained stress response elements, hormone response elements, light response elements and multi-factor response elements, and light response elements was the most abundant (142 elements). Expression analysis showed that the expression levels of CsCCD1 and CsCCD4 in elder leaves were higher than those in younger leaves and stems. With the increase of turning over times, the expression levels of CsCCD1 and CsCCD4 decreased, while supplementary LED light strongly promoted their expression levels in the early stage. The expression level of NCED in younger leaves was higher than that in elder leaves and stems on average, and the expression trend varied in the process of turning over. NCED3 first increased and then decreased, with an expression level 15 times higher than that in fresh leaves. In the late stage of turning over, supplementary LED light significantly promoted its gene expression. In conclusion, CsCCD gene family member expressions were regulated by mechanical force and light. These understandings may help to optimize tea processing techniques and improve tea quality.