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严重的种子败育是影响珙桐自然繁殖的重要原因之一,调控种子败育的分子机制及关键基因目前尚不清楚。根据本研究小组前期获得的珙桐种子转录组数据,筛选到22个转录本,分属14个纤维素合酶Ces A编码基因,所有转录本在败育种子中均呈现上调表达趋势。分析珙桐种子中的纤维素含量发现,正常种子在发育过程中纤维素含量持续升高,而在败育种子中纤维素含量显著高于正常种子。挑选4个在败育种子中显著上调的Ces A基因进行q PCR分析,结果表明它们表达模式相似,在败育种子中表达量均显著高于正常种子,且在正常种子发育后期上调表达。挑选其中表达差异最显著的c43681.graph_c0进行克隆获得882 bp片段。经序列比对,其编码产物包含292个氨基酸,与拟南芥纤维素合酶Ces A4同源性最高。分析c43681.graph_c0在珙桐不同组织中的表达量发现,该基因在茎中表达量较低,而在果肉中表达量较高,在败育种子中表达量显著高于其它组织。本研究筛选到的c43681.graph_c0可能是一个在珙桐生殖器官中调控纤维素合成的关键基因。
Severe seed abortion is one of the important factors that affect the natural reproduction of Davidia involucrata. The molecular mechanisms and key genes regulating seed abortion are not clear at present. Based on the data from the seedlings transcriptome of Davidia involucrata collected in the previous study, 22 transcripts were screened, belonging to 14 Ces A genes. All the transcripts showed up-regulated expression in the aborted seeds. Analysis of the content of cellulose in Davidia involucrata seeds showed that the content of cellulose in normal seeds increased continuously while the content of cellulose in aborted seeds was significantly higher than that in normal seeds. Q-PCR analysis of four Ces A genes that were significantly up-regulated in aborted seeds showed that their expression pattern was similar and their expression levels in aborted seeds were significantly higher than those in normal seeds and up-regulated in normal seed development. The c43681.graph_c0 with the most significant difference in expression was selected for cloning to obtain a 882 bp fragment. Sequence alignment showed that the encoded product contained 292 amino acids, which had the highest homology with Ces A4 of Arabidopsis cellulose synthase. Analysis of c43681.graph_c0 expression in different tissues of Davidia involucrata showed that the expression level of c43681.graph_c0 was lower in stems and higher in pulp than in other tissues. The c43681.graph_c0 screened in this study may be a key gene regulating cellulose synthesis in the genus Davidia.