水稻穗长基因PAL3的克隆及自然变异分析

Map-based Cloning and Natural Variation Analysis of the PAL3 Gene Controlling Panicle Length in Rice

穗型是决定水稻(Oryza sativa)产量的关键因素之一。我们从粳稻品种圣稻808 (SD808)的EMS诱变突变体库中发现4份短穗突变体,这些突变体的穗长、一级枝梗数、二级枝梗数和穗粒数发生不同程度的降低。基因定位和图位克隆表明,这些突变体的表型受同一基因控制,将该基因命名为PAL3 (PANICLE LENGTH3)。PAL3编码一个含12个跨膜结构域的多肽转运蛋白。pal3-1和pal3-2的点突变造成保守区域的氨基酸发生非同义突变;pal3-3的点突变造成第1外显子和内含子拼接错误;pal3-4的点突变造成蛋白翻译提前终止,导致第12个跨膜域缺失。对PAL3进行单倍型分析,共鉴定出9个单倍型(Hap1–Hap9),其中Hap1–Hap3为主要单倍型。Hap1以粳稻为主,Hap2同时包含籼稻和粳稻,Hap3则以籼稻为主。Hap1起源于普通野生稻(O. rufipogon), Hap2和Hap3可能起源于一年生普通野生稻(O. nivara)。统计分析结果表明, Hap3的穗长显著高于Hap1和Hap2,其具有提高穗长的潜力。该研究揭示了多肽转运蛋白对水稻穗型的重要调控作用,为水稻穗型改良奠定了理论基础。

Panicle architecture is one of the key factors determining the rice(Oryza sativa) grain yield. In this study, four short panicle mutants were identified from an EMS(ethyl methane sulfonate) mutant library of a japonica vareity Shengdao 808(SD808). The panicle length, primary branch number, secondary branch number and grain number per panicle of these mutants were decreased in various degrees. Map-based cloning showed that these mutants were controlled by the gene PAL3(PANICLE LENGTH 3) which encodes a peptide transporter with 12 transmembrane domains.The point mutations of pal3-1 and pal3-2 resulted in non-synonymous mutations of amino acids in the conserved region;the point mutation of pal3-3 resulted in the mis-splicing of the first exon and intron;and the point mutation of pal3-4 resulted in the premature termination of translation and thus the deletion of the 12 th transmembrane domain. Through haplotype analysis, nine haplotypes of PAL3 were identified, including three major haplotypes(Hap1–Hap3). Hap1 is dominated by japonica accessions, Hap2 contains both indica and japonica accessions, while Hap3 is dominated by indica accessions. Hap1 originated from O. rufipogon, while Hap2 and Hap3 may originate from O. nivara. Statistical analysis showed that the panicle length of Hap3 was significantly higher than that of Hap1 and Hap2, indicating that Hap3 may have the potential to improve the panicle length. In conclusion, this study revealed the important role of the peptide transporter in regulating rice panicle architecture and thus provides a new theoretical basis for rice panicle architecture improvement.