可可蔗糖磷酸合成酶基因家族进化及组织表达分析

Phylogeny and Expression Profile of the Sucrose Phosphate Synthase Gene Family in Cacao(Theobroma cacao L.)

在高等植物中,蔗糖磷酸合成酶（Sucrose phosphate synthase,SPS）是蔗糖合成的限速酶。在多种植物中都发现了SPS基因,而可可中尚未见相关报道。通过分析可可基因组数据库,鉴定出4个SPS候选基因,依次命名为TcSPS1、TcSPS2、TcSPS3和TcSPS4。4个基因的编码区（CDS）长度在3 075~3 228 bp之间,外显子数目为12~14,预测蛋白的平均分子量为118.15 ku,等电点均小于7。进化分析结果表明SPS基因家族分成3个亚族;TcSPS1和TcSPS2属于ClassⅠ亚族,TcSPS3和TcSPS4分别属于ClassⅡ亚族和ClassⅢ亚族。实时荧光定量PCR分析结果表明,TcSPS1与TcSPS2在树皮和果实中高量表达,TcSPS3和TcSPS4主要在叶片中表达。伴随着叶片和花蕾生长发育,各TcSPS基因表达量均呈现出上升的趋势,表明其与主要光合产物--蔗糖的合成或再合成有密切联系,参与可可“源库”器官中光合产物分配。

In higher plants, sucrose phosphate synthase （SPS） is widely considered as a key gene for sucrose synthesis. Although several paralogous genes encoding different isozymes of SPS have been identified and characterized in multiple plant genomes, detailed information about the SPS genes is still lacking for cacao. The study reported that the identification of four novel SPS genes from economically important cacao tree were designated as TcSPS1, TcSPS2, TcSPS3 and TcSPS4. Sequences analyses revealed that CDS of TcSPS1-4 were ranging from 3 075 bp to 3 228 bp, containing 12-14 exous. The average molecular weight of four predicted protein were 118.15 ku, and pIs of all proteins were less than 7. The expression patterns of the cacao SPS genes were investigated via Real-time PCR in various tissues, different developmental phases of leaf, flower bud. TcSPS1 and TcSPS2 were highly expressed in the bark and pods; TcSPS3 and TcSPS4 were predominantly expressed in the leaves. The transcription levels of TcSPS genes were continuously increased along with the leaf and flower bud development. These results indicated that TcSPS genes were significantly related with sucrose synthesis or re- synthesis in source and sink organs, and participate in photoassimilate translocation.