The papaya diminutive mutant exhibits miniature stature, retarded growth and reduced fertility. This undesirable mutation appeared in the variety 'Sunset', the progenitor of the transgenic line 'SunUp', and was accidentally carried forward into breeding populations. The diminutive mutation was mapped to chromosome 2 and fine mapped to scaffold 25. Sequencing of a bacterial artificial chromosome in the fine mapped region led to the identification of the target gene responsible for the diminutive mutant, a gene orthologous to MMS19 with a 36.8 kb deletion co-segregating with the diminutive mutant. The genomic sequence of CpMMS19 is 62 kb, consisting of 20 exons and 19 introns. It encodes a protein of 1143 amino acids while the diminutive allele encodes a truncated protein of 287 amino acids. Expression of the full-length CpMMS19 was able to complement the thermosensitive growth of the yeast mms19 deletion mutant while expression of the diminutive allele resulted in increased thermosensitivity. Over-expression of the diminutive allele in Arabidopsis met18 mutant results in a high frequency of seed abortion. The papaya diminutive phenotype is caused by an alteration in gene function rather than a loss-of-function mutation. SCAR (sequence characterized amplified region) markers were developed for rapid detection of the diminutive allele in breeding populations.

中文翻译：

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木瓜小型突变体的定位克隆和表征揭示了 CpMMS19 基因中的截断突变。

木瓜小型突变体表现出身材矮小、生长迟缓和生育力下降。这种不受欢迎的突变出现在转基因品系“SunUp”的祖先品种“Sunset”中，并且意外地被带到了繁殖种群中。微小突变被定位到染色体 2 并精细定位到支架 25。在精细定位区域中对细菌人工染色体进行测序导致鉴定了负责微小突变体的靶基因，该基因与 MMS19 直系同源，具有 36.8 kb 缺失与小型突变体共同分离。CpMMS19的基因组序列为62 kb，由20个外显子和19个内含子组成。它编码1143个氨基酸的蛋白质，而小型等位基因编码287个氨基酸的截短蛋白质。全长 CpMMS19 的表达能够补充酵母 mms19 缺失突变体的热敏性生长，而小型等位基因的表达导致热敏性增加。拟南芥met18突变体中小型等位基因的过度表达导致种子流产的频率很高。木瓜小型表型是由基因功能的改变而不是功能丧失突变引起的。SCAR（序列特征扩增区域）标记被开发用于快速检测繁殖种群中的小型等位基因。木瓜小型表型是由基因功能的改变而不是功能丧失突变引起的。SCAR（序列特征扩增区域）标记被开发用于快速检测繁殖种群中的小型等位基因。木瓜小型表型是由基因功能的改变而不是功能丧失突变引起的。SCAR（序列特征扩增区域）标记被开发用于快速检测繁殖种群中的小型等位基因。