Advanced Laboratory for Plant Genetic Engineering (formerly IIT-BREF Biotek), Indian Institute of Technology, Kharagpur-721302, India.
BMC Plant Biol. 2010 Mar 2;10:39. doi: 10.1186/1471-2229-10-39.
The application of hybrid rice technology has significantly increased global rice production during the last three decades. Approximately 90% of the commercially cultivated rice hybrids have been derived through three-line breeding involving the use of WA-CMS lines. It is believed that during the 21st century, hybrid rice technology will make significant contributions to ensure global food security. This study examined the poorly understood molecular basis of the WA-CMS system in rice.
RFLPs were detected for atp6 and orfB genes in sterile and fertile rice lines, with one copy of each in the mt-genome. The RNA profile was identical in both lines for atp6, but an additional longer orfB transcript was identified in sterile lines. 5' RACE analysis of the long orfB transcript revealed it was 370 bp longer than the normal transcript, with no indication it was chimeric when compared to the genomic DNA sequence. cDNA clones of the longer orfB transcript in sterile lines were sequenced and the transcript was determined unedited. Sterile lines were crossed with the restorer and maintainer lines, and fertile and sterile F1 hybrids were respectively generated. Both hybrids contained two types of orfB transcripts. However, the long transcript underwent editing in the fertile F1 hybrids and remained unedited in the sterile lines. Additionally, the editing of the 1.1 kb orfB transcript co-segregated with fertility restoring alleles in a segregating population of F2 progeny; and the presence of unedited long orfB transcripts was detected in the sterile plants from the F2 segregating population.
This study helped to assign plausible operative factors responsible for male-sterility in the WA cytoplasm of rice. A new point of departure to dissect the mechanisms governing the CMS-WA system in rice has been identified, which can be applied to further harness the opportunities afforded by hybrid vigor in rice.
在过去的三十年中，杂交水稻技术的应用显著提高了全球水稻产量。大约 90%的商业化种植的水稻杂种是通过涉及使用 WA-CMS 系的三系育种获得的。人们相信，在 21 世纪，杂交水稻技术将为确保全球粮食安全做出重大贡献。本研究探讨了水稻中 WA-CMS 系统的分子基础。
在不育和可育水稻系中检测到 atp6 和 orfB 基因的 RFLP，mt 基因组中各有一个拷贝。atp6 在两条线中具有相同的 RNA 谱，但在不育系中鉴定出另一个更长的 orfB 转录本。对长 orfB 转录本的 5'RACE 分析表明，它比正常转录本长 370bp，与基因组 DNA 序列相比，没有表明它是嵌合的。不育系中较长 orfB 转录本的 cDNA 克隆被测序，转录本被确定未编辑。不育系与恢复系和保持系杂交，分别产生可育和不育 F1 杂种。两种杂种都含有两种类型的 orfB 转录本。然而，长转录本在可育 F1 杂种中发生编辑，而在不育系中未编辑。此外，orfB 1.1kb 转录本的编辑与 F2 后代分离群体中的育性恢复等位基因共分离；并且在来自 F2 分离群体的不育植物中检测到未编辑的长 orfB 转录本。
本研究有助于确定水稻 WA 细胞质雄性不育的合理作用因素。已经确定了一个新的起点来剖析水稻 CMS-WA 系统的调控机制，这可以应用于进一步利用水稻杂种优势提供的机会。
