Seed loss resulting from pod shattering is a major constraint in production of oilseed rape (Brassica napus L.). However, the molecular mechanisms underlying pod shatter resistance are not well understood. Here, we show that the pod shatter resistance at quantitative trait locus qSRI.A9.1 is controlled by one of the B. napus SHATTERPROOF1 homologs, BnSHP1.A9, in a doubled haploid population generated from parents designated R1 and R2 as well as in a diverse panel of oilseed rape. The R1 maternal parental line of the doubled haploid population carried the allele for shattering at qSRI.A9.1, while the R2 parental line carried the allele for shattering resistance. Quantitative RT-PCR showed that BnSHP1.A9 was expressed specifically in flower buds, flowers, and developing siliques in R1, while it was not expressed in any tissue of R2. Transgenic plants constitutively expressing either of the BnSHP1.A9 alleles from the R1 and R2 parental lines showed that both alleles are responsible for pod shattering, via a mechanism that promotes lignification of the enb layer. These findings indicated that the allelic differences in the BnSHP1.A9 gene per se are not the causal factor for quantitative variation in shattering resistance at qSRI.A9.1. Instead, a highly methylated copia-like long terminal repeat retrotransposon insertion (4803 bp) in the promotor region of the R2 allele of BnSHP1.A9 repressed the expression of BnSHP1.A9, and thus contributed to pod shatter resistance. Finally, we showed a copia-like retrotransposon-based marker, BnSHP1.A9_R2, can be used for marker-assisted breeding targeting the pod shatter resistance trait in oilseed rape.

中文翻译：

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在SHATTERPROOF1基因BnSHP1.A9上游区域中出现的类似仿生的反转录转座子与油菜中荚果抗裂性的定量变化有关。

荚果破碎造成的种子损失是油菜（甘蓝型油菜）生产中的主要制约因素。但是，对荚果抗碎性的分子机制尚不十分了解。在这里，我们表明，在荚果落粒抗性数量性状基因座qSRI.A9.1由之一控制欧洲油菜SHATTERPROOF1同系物，BnSHP1.A9，在从父母产生双单倍体群体指定的R1和R2，以及在各种各样的油菜。双倍单倍体群体的R1亲本亲本系在qSRI.A9.1携带了等位基因用于粉碎，而R2亲本系则携带了抗粉碎性的等位基因。定量RT-PCR显示BnSHP1.A9在R1的花蕾，花朵和发育中的角果树中特异性表达，而在R2的任何组织中均不表达。组成型表达来自R1和R2亲本系的BnSHP1.A9等位基因的转基因植物表明，这两个等位基因都是通过促进en b层木质化的机制导致荚果碎裂。这些发现表明，BnSHP1.A9基因本身的等位基因差异并不是qSRI.A9.1的抗破碎性定量变化的原因。而是高度甲基化的鸦片样长末端重复反转录转座子插入（4803碱基对）中的R2等位基因的启动子区BnSHP1.A9压抑的表达BnSHP1.A9，从而促成了荚果落粒抗性。最后，我们显示出COPIA样基于反转录转座子标记物，BnSHP1.A9 _R2，可以用于标记辅助的育种靶向油菜的荚果落粒抗性性状。