两个棉花HyPRP基因的分子鉴定与初步表达分析

从棉花胚珠和纤维cDNA文库中分离了2个编码杂合的富含脯氨酸的细胞壁蛋白（hybrid proline-rich protein, HyPRP）基因，命名为GhHyPRP1和GhHyPRP2，其编码蛋白分别含有327和137个氨基酸。蛋白质结构分析表明，二者都含有: N-端信号肽区、富含脯氨酸结构域、和C-端含有特定排列顺序和数目的半胱氨酸结构域。根据蛋白质结构域组成特点及与其他多结构域的富含脯氨酸蛋白质序列的同源性比较分析，将GhHyPRP1归为HyPRP A类蛋白质，将GhHyPRP2归为HyPRP B类蛋白质。RT-PCR分析显示GhHyPRP1在幼苗下胚轴中大量表达，而GhHyPRP2在胚珠中优势表达，暗示这2个基因可能分别在棉花不同组织发育中具有一定的生物学功能。

Molecular Characterization and Expression Analysis of Two Genes Encoding Hybrid Proline-Rich Proteins in Cotton

We identified two cDNAs (designated as GhHyPRP1 and GhHyPRP2) encoding putative cell wall hybrid proline-rich proteins (HyPRPs) from cotton (Gossypium hirsutum) ovule and fiber cDNA libraries. GhHyPRP1 and GhHyPRP2 encode 327 and 137 amino acids, respectively. Both GhHyPRP1 and GhHyPRP2 proteins have the same overall primary structure: an amino-terminal signal peptide; a central proline-rich domain that contains nine copies of 13 peptide repeat for GhHyPRP1 (similar to PPTYAPPPKSPSK), and 10 copies of double peptide repeat for GhHyPRP2 (similar to CP); and a carboxy-terminal nonrepetitive domain with a certain number and specific distribution of cysteines which is in GhHyPRP1 six cysteines and a typical eight-cysteine motif (8CM) in GhHyPRP2. Based on the protein domain organization and protein similarity, GhHyPRP1 was grouped into the HyPRP class A proteins, while GhHyPRP2 into the HyPRP class B proteins of higher plants. Phylogenetic relationship alalysis clearly showed that GhHyPRP1 and GhHyPRP2 were separated into two subgroups, in the top of different clade respectively, demonstrating that they were evolutionally far related which are consistent with the results based on protein domain organization and protein similarity analysis. Expression analysis of the two GhHyPRPs was carried out by quantitative realtime RT-PCR. The results showed that GhHyPRP1 was highly expressed in hypocotyls, while GhHyPRP2 expressed preferentially in 10 DPA ovule. The results suggest that GhHyPRP1 and GhHyPRP2 may play a role in the development of different cotton tissues.