Identification,bioinformatics and expression analysis of taro starch synthase gene family
[Objective]The study aimed to identify a family of starch synthase(SS)genes in the taro genome and analyze their bioinformatics and expression patterns to provide a basis for genetic improvement of yield,quality and nutritional traits in taro.[Method]HMMER 3.12b software was used to identify the SS gene family information in the taro genome using the conserved structural domain Glyco_transf_5 as a model,and bioinformatics softwares were used to analyze its molecular structural features,phylogenetic relationships and cis-acting elements.Transcriptomic and real-time fluorescent quantitative PCR techniques were used to detect its transcriptional expression under normal growth and development conditions and drought stress.[Result]Six SS genes(CeSS1,CeSS2,CeSS3-1,CeSS3-2,CeSS4 and CeGBSS1)were i-dentified in the taro genome.The six predicted taro SS genes ranged in length from 4980 to 61 347 bp,corresponding to coding DNA se-quence(CDS)lengths from 1275 to 2895 bp,with the number of amino acid residues encoding the protein ranging from 424 to 964,molecu-lar weight from 48 067.43 to 109 391.75 Da,and isoelectric points from 5.18 to 6.11.Phylogenetic analysis revealed that the six taro SS proteins were divided into five subfamilies.Genetic structure analysis showed that the number of exons in the six taro SS genes ranged from 7 to 15.Ten conserved motifs were identified in six CeSS proteins,seven of which were annotated.Conservative structural domain analysis showed that CeSS1,CeSS2,CeSS4 and CeGBSS1 proteins all had starch synthase catalytic domain(motif 2 and motif 5)and glycosyl trans-ferase group 1(motif 1 and motif 3),while CeSS3-1 protein had motif 1,motif 3 and motif 5 and CeSS3-2 protein had only motif 2.Analy-sis of the cis-acting elements in the promoter region of the gene showed that a total of 73 cis-acting elements were predicted,36 of which were functionally annotated and involved a large number of elements related to light response,hormone response,stress response and growth and development,in addition to the core elements TATA-box and CAAT-box.Under normal growth and development conditions,the overall ex-pression of the six CeSS genes was higher in leaves and corms than in petioles and roots,with the expression of CeGBSS1 being much higher than the rest of the genes and the relative expression in leaves and corms reaching extremely significant levels(P＜0.01,the same as be-low).At different developmental stages of the corm,CeGBSS1 had high expression at all developmental stages and showed a tendency to in-crease during 30-90 days,while the expression of the remaining genes was low.Under drought stress,the relative expression of six CeSS genes in leaves was significantly(P＜0.05)or extremely significantly(P＜0.01)reduced compared with control.[Conclusion]Six SS genes were identified in the taro genome and their molecular structural features and expression patterns were clarified,among which CeGBSS1 may be a key gene for starch biosynthesis in taro.
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