EXO70在拟南芥和水稻基因组中的倍增

Comparison of EXO70 duplication between Arabidopsis thaliana and Oryza sativa

作为胞泌复合体的一个重要组件,EXO70在人类、小鼠及酵母中均由单基因编码.为研究EXO70在拟南芥和水稻基因组中倍增的异同,从拟南芥和水稻基因组中钓取所有的EXO70家族基因,分析后发现,拟南芥中包含23个EXO70基因,其中15个基因位于染色体的负链;选择性剪接的存在共产生27种成熟的m RNA.水稻中共发现47个EXO70基因座,它们分别分散于12条染色体的正负链,其中的29个基因位于正链;分别包含Os EXO70H3和Os EXO70H4在内的11号染色体和12染色体的5′端存在一段约2×106 bp区段的序列高度同源;Os EXO70基因倍增的复杂性高于拟南芥EXO70.EXO70基因在拟南芥和水稻中均存在密码子使用偏好性,At EXO70和Os EXO70的密码子偏好性存在较大的差异.Pfam03081是EXO70蛋白质共有的结构域,且在三维结构上极为保守,这可能决定不同的EXO70蛋白存在相同或相近的功能.结果表明,EXO70在拟南芥和水稻2个物种进化中均存在多次加倍,Os EXO70倍增的次数、方式和复杂性都高于At EXO70;高度保守的Pfam03081可能是决定EXO70蛋白功能的关键因素;像其他基因一样,EXO70同义密码子的偏性模式存在明显的物种特异性.

EXO70, an important component of the exocyst complex, is encoded by a single gene in humans, mice and yeast. To understand EX070 gene duplication in plant genomes, we identified and analyzed all OsEX070 and AtEX070 genes in Arabidopsis thaliana and Oryza sativa. A total of 23 different EX070 genes were identified in the A. thaliana genome, of which 15 were present on the ＇-＇ strand. We detected 27 different mature mRNAs of EX070 arising from alternative splicing. In O. sativa, 38 OsEX070 genes coding for proteins comprising more than 412 amino acids were found to be distributed across the 12 rice chromosomes. Of these genes, 29 were located on the ＇＋＇ strand. Interestingly, a product of large-scale genome duplication--an approximately 2-Mbp-long fragment including both OsEXO7OH3 and OsEXO7OH4, was highly conserved between chromosomes 11 and 12. The gene duplication mode of OsEX070 is more complex than that of AtEX070. Although synonymous codon bias exists in both AtEX070 and OsEX070, codon preferences differ between them. All EXO70 proteins contain a pfam03081 domain, indicating that these proteins may have the same or similar functions. We conclude that EX070 has been duplicated multiple times during the evolution of both A. thaliana and O. sativa, with more duplications occurring in O. sativa than in A. thaliana. Additionally, a greater number of gene duplication mechanisms are operative for OsEX070 than for AtEX070. We also propose that the pfam03081 domain may play an essential role in EXO70 functional determination. Finally, many differences in synonymous codon preference exist between AtEX070 and OsEX070.