Genetic factors responsible for the mobility of mPing in the rice genome

在含有Rurm1(水稻泛素相关修饰物-1)等位基因的突变系IM294(细长颖壳突变体)中，mPING插入失活的突变株Rurm1(Rurm1^m)的mPING有很高的剪切率(约1.1%)。与原始品种Gimbozu相比，Ping的两个ORF在IM294中的表达水平也较高。为了弄清相同遗传背景下Rurm1的功能与Ping活性的关系，通过轮回回交，将Rurm1的突变等位基因导入到银杏背景中。此外，还利用了分离于IM294系中的1对非细长颖片株系(Rurm1^+/Rrum1^+)和细长颖片株系(Rurm1^m/Rurm1^m)。与Gimbozu及其等基因系和同胞系相比，失活的Rurm1和mPING插入增强了Ping的两个ORF的表达水平。而Pong基因的表达水平未见明显变化。这些结果表明，Rurm1的失活通过增强Ping‘s ORF的表达促进了mPING的切除。虽然转座子的失活通常受甲基化的调节，但RURM1蛋白不太可能直接调节DNA的甲基化。用安捷伦公司的22K-微阵列分析了Rurm1等位基因失活的影响。Rurm1的失活上调了核糖体和细胞核中蛋白质生物合成相关基因的表达。它还下调了与代谢和生理过程相关的基因的表达。这些结果表明，Rurm1的功能与大量与生理过程相关的基因转录有关。蛋白质合成相关基因的上调预示着植物对生长迟缓的补偿。还观察到与DNA修复过程相关的基因上调，表明mPING切除IM294导致频繁的DNA双链断裂。

In a mutant line IM294 (slender glume mutant) which harbors Rurm1 (Rice Ubiquitine Related Modifier-1) allele inactivated by mPing insertion shows high excision frequency (ca.1%) of mPing from mutant Rurm1 allele (Rurm1^m). Expression levels of two ORFs of Ping were also high in IM294 comparing to the original variety Gimbozu. To clarify the relation between the function of Rurm1 and Ping activity under the same genetic background, the mutant allele of Rurm1 was introduced into Gimbozu background through recurrent backcrossing. Also, a pair of non-slender glume line (Rurm1^+/Rrum1^+) and slender glume line (Rurm1^m/Rurm1^m) derived from offspring of the non-slender glume plant (Rurm1^+/Rurm1^m) segregated among IM294 line were used. Comparing the Gimbozu and its isogenic line and sib lines, inactivation of Rurm1 with mPing insertion enhanced the expression levels of two ORFs of Ping. On the other hand, significant change in the expression level of Pong was not observed. These indicate that the inactivation of Rurm1 promotes the mPing excision by enhancing the expression of Ping's ORFs. Though, the inactivation of transposon is generally regulated by methylation, it is quite unlikely that RURM1 protein directly regulate the methylation of DNA. Effect of the inactivation of Rurm1 allele was also analyzed using 22k-micro array (Agilent Co.,). Inactivation of Rurm1 upregulate the expression of protein biosynthesis related genes in ribosome and nucleus. It also downregulated the expression of genes related to metabolism and physiological process. These indicate that the function of Rurm1 is related to transcription of vast number of genes related to the physiological process. Upregulation of protein synthesis related genes indicates the compensation to growth retardation of plants. Upregulation of genes related to DNA-repair process was also observed indicating the frequent DNA double strands break induced by mPing excision in IM294.