Lloyd Andrew H, Milligan Andrew S, Langridge Peter, Able Jason A
School of Agriculture, Food & Wine, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, South Australia, 5064, Australia.
BMC Plant Biol. 2007 Dec 20;7:67. doi: 10.1186/1471-2229-7-67.
Chromosome pairing, recombination and DNA repair are essential processes during meiosis in sexually reproducing organisms. Investigating the bread wheat (Triticum aestivum L.) Ph2 (Pairing homoeologous) locus has identified numerous candidate genes that may have a role in controlling such processes, including TaMSH7, a plant specific member of the DNA mismatch repair family.
Sequencing of the three MSH7 genes, located on the short arms of wheat chromosomes 3A, 3B and 3D, has revealed no significant sequence divergence at the amino acid level suggesting conservation of function across the homoeogroups. Functional analysis of MSH7 through the use of RNAi loss-of-function transgenics was undertaken in diploid barley (Hordeum vulgare L.). Quantitative real-time PCR revealed several T0 lines with reduced MSH7 expression. Positive segregants from two T1 lines studied in detail showed reduced MSH7 expression when compared to transformed controls and null segregants. Expression of MSH6, another member of the mismatch repair family which is most closely related to the MSH7 gene, was not significantly reduced in these lines. In both T1 lines, reduced seed set in positive segregants was observed.
Results presented here indicate, for the first time, a distinct functional role for MSH7 in vivo and show that expression of this gene is necessary for wild-type levels of fertility. These observations suggest that MSH7 has an important function during meiosis and as such remains a candidate for Ph2.
染色体配对、重组和DNA修复是有性生殖生物减数分裂过程中的基本过程。对普通小麦(Triticum aestivum L.)的Ph2(同源配对)位点进行研究,已鉴定出许多可能在控制这些过程中发挥作用的候选基因,包括TaMSH7,它是DNA错配修复家族的植物特异性成员。
对位于小麦3A、3B和3D染色体短臂上的三个MSH7基因进行测序,结果显示在氨基酸水平上没有明显的序列差异,这表明同源群之间功能保守。通过使用RNAi功能丧失转基因技术对二倍体大麦(Hordeum vulgare L.)中的MSH7进行了功能分析。定量实时PCR显示,有几个T0系的MSH7表达降低。对详细研究的两个T1系的阳性分离株进行分析,结果显示与转化对照和无效分离株相比,它们的MSH7表达降低。错配修复家族中与MSH7基因关系最密切的另一个成员MSH6的表达在这些系中没有显著降低。在两个T1系中,均观察到阳性分离株的结实率降低。
本文给出的结果首次表明MSH7在体内具有独特的功能作用,并表明该基因的表达对于野生型育性水平是必需的。这些观察结果表明,MSH7在减数分裂过程中具有重要功能,因此仍是Ph2的候选基因。