扩展蛋白是植物细胞壁的重要组成部分,具有松驰细胞壁和增加细胞壁柔韧性的作用,在植物的生长发育及抗性等方面起到重要的作用。水稻的全基因组序列统计分析显示,水稻扩展蛋白基因家族包含58个成员,分属于A(34)、B(19)、LA(4)和LB(1)4个亚家族,分布在水稻10条染色体上的58个位点,且同一亚家族成员有成簇存在的现象。扩展蛋白基因长度范围为687~1128 bp,编码蛋白质具有保守的结构域,以及保守的半胱氨酸和色氨酸残基。多数情况下,亚家族成员之间的氨基酸一致率小于35%,而同一亚家族成员之间的氨基酸一致率大于35%。在内含子、外显子组成模式上,水稻扩展蛋白呈现明显的亚家族特异性,除个别基因以外,A类基因含有1或2个内含子,B类含有3个内含子,LA和LB类含有4个内含子。密码子使用统计显示,与其他物种相比,水稻中的扩展蛋白具有更多的密码子使用偏好性,有26个高频密码子存在。研究结果展示了水稻扩展蛋白基因家族的基本信息,为深入研究扩展蛋白基因的功能、探讨物种间的进化关系奠定基础。
Expansin refers to a family of nonenzymatic proteins found in the plant cell wall with important roles in plant cell growth, developmental processes, and resistance to stress. Whole rice genome sequencing revealed that it contains 58 expansin genes, which belong to 4 subfamilies (A (34), B (19), LA (4) and LB (1)). All the genes were located on 10 of 12 rice chromosomes where several subfamily members clustered. Each of expansin genes ranged from 687 bp to 1128 bp in size. Sequence alignment showed that all expansins had three structural domains with two conserved amino acids of cystine in N-terminus and tryptophan in C-terminus. The amino acid identity of members among different subfamilies was less than 35%, while that among the same subfamily was more than 35%. Most genes of A subfamily had 1 or 2 introns, while genes of B, LA and LB subfamily had 3, 4 and 4 introns, respectively. Statistics analysis of codon usage showed that expansins in rice have 26 high-frequency codons which are more biased than those in other species. These bioinformatics findings will be helpful for the further study of the function and evolution of expansin genes.
[1] DJ. Loosening of plant cell walls by expansins. Nature , 2000, 407(6802): 321-326.
[2] DJ. Growth of the plant cell wall. Nat Rev Mol Cell Biol , 2005, 6(11): 850-861.
[3] HT, Kende H. Expansins and internodal growth of deepwater rice. Plant Physiol , 2001, 126(4): 1471-1479.
[4] HT, Kende H. Expansins in deepwater rice internodes. Plant Physiol , 1997, 113(4): 1137-1143.
[5] DJ. Characterization of long-term extension of isolated cell walls from growing cucumber hypocotyls. Planta , 1989, 177(1): 121-130.
[6] Y, Kende H. Expression of β-expansins is correlated with elongation of internodes in deepwater rice. Plant Physiol , 2001, 127(2): 645-654.
[7] S, Durachko DM, Cosgrove DJ. Two endogenous proteins that induce cell wall extension in plant. Plant Cell , 1992, 4(11): 1425-1433.
[8] HT, Kende H. Expression of expansin genes is correlated with growth in deepwater rice. Plant Cell , 1997, 9(9): 1661-1671.
[9] DJ, Li LC, Cho HT, Hoffmann-Benning S, Moore RC, Blecker D. The growing world of expansins. Plant Cell Physiol , 2002, 43(12): 1436-1444.
[10] WG, Tao J, Zhou XR, Yang WY. Characteristics of expansins insoybean ( Glycine max ) internodes and responses to shade stress. Asian J Crop Science , 2011, 3(1): 26-34.
[11] Y, Kende H. Expression of α-expansin and expansin-like genes in deepwater rice. Plant Physiol , 2002, 130(3): 1396-1405.
[12] D, Lee Y, Cho HT, Kende H. Regulation of expansin gene expression affects growth and development in transgenic rice plants. Plant Cell , 2003, 15(6): 1386-1398.
[13] J, Takano T, Akita S. Expression of α-expansin genes in young seedlings of rice ( Oryza sativa L.). Planta , 2000, 211(4): 467-473.
[14] Y, Choi D. Biochemical properties and localization of the β-expansin OsEXPB3 in rice ( Oryza sativa L.). Mol Cell , 2005, 20(1): 119-126.
[15] L, Kudahettige RL, Alpi A, Perata P. Expansin gene expression and anoxic coleoptile elongation in rice cultivars. J Plant Physiol , 2009, 166(14): 1576-1580.
[16] HT, Cosgrove DJ. Regulation of root hair initiation and expansin gene expression in Arabidopsis . Plant Cell , 2002, 14(12): 3237-3253.
[17] ZM, Kang B, He XW, Lv SL, Bai YH, Ding WN, Chen M, Cho HT, Wu P. Root hair-specific expansins modulate root hairelongation in rice. Plant J , 2011, 66(5): 725-734.
[18] HT, Kende H. Tissue localization of expansins in deepwater rice. Plant J , 1998, 15(6): 805-812.
[19] W, Zhao J, Li X, Qin L, Yan X, Liao H. A soybean β-expansin gene GmEXPB2 intrinsically involved in root system architecture responses to abiotic stresses. Plant J , 2011, 66(3): 541-552.
[20] JH, Jeong DH, Park MC, An G. Characterization and transcriptional expression of the α-expansin gene family in rice. Mol Cells , 2005, 20(2): 210-218.
[21] L, Zheng B, Mao C, Qi X, Liu F, Wu P. Analysis of transcripts that are differentially expressed in three sectors of the rice root system under water deficit. Mol Genet Genomics , 2004, 272(4): 433-442.
[22] YJ, Thorne ET, Sharp RE. Modification of expansin transcript levels in the maize primary root at low water potentials. Plant Physiol , 2001, 126(4): 1471-1479
[23] AJ, McQueen-Mason S, Mandel T, Kuhlemeier C. Induction of leaf primordia by the cell wall protein expansin. Science , 1997, 276(5317): 1415-1418.
[24] HT, Cosgrove DJ. Altered expression of expansin modulates leaf growth and pedicel abscission in Arabidopsis th a liana . Proc Natl Acad Sci USA , 2000, 97(17): 9783-9788.
[25] E, Cosgrove DJ. Expansins in growing tomato leaves. Plant J , 1995, 8(6): 795-802.
[26] GM, Mellerowicz EJ, Abe H, Schrader J, Winzéll A, Sterky F, Blomqvist K, McQueen-Mason S, Teeri TT, Sundberg B. Expansins abundant in secondary xylem belong to subgroup a of the α-expansin gene family. Plant Physiol , 2004, 135(3): 1552-1564.
[27] MC, Pombo MA, Mart�
