Chueasiri Chutharat, Chunthong Ketsuwan, Pitnjam Keasinee, Chakhonkaen Sriprapai, Sangarwut Numphet, Sangsawang Kanidta, Suksangpanomrung Malinee, Michaelson Louise V, Napier Johnathan A, Muangprom Amorntip
National Center for Genetic Engineering and Biotechnology, Thailand Science Park, Klong Luang, Pathumthani, Thailand.
Biological Chemistry Department, Rothamsted Research, Harpenden, Hertfordshire, United Kingdom.
PLoS One. 2014 Sep 5;9(9):e106386. doi: 10.1371/journal.pone.0106386. eCollection 2014.
The orosomucoids (ORM) are ER-resisdent polypeptides encoded by ORM and ORMDL (ORM-like) genes. In humans, ORMDL3 was reported as genetic risk factor associated to asthma. In yeast, ORM proteins act as negative regulators of sphingolipid synthesis. Sphingolipids are important molecules regulating several processes including stress responses and apoptosis. However, the function of ORM/ORMDL genes in plants has not yet been reported. Previously, we found that temperature sensitive genetic male sterility (TGMS) rice lines controlled by tms2 contain a deletion of about 70 kb in chromosome 7. We identified four genes expressed in panicles, including an ORMDL ortholog, as candidates for tms2. In this report, we quantified expression of the only two candidate genes normally expressed in anthers of wild type plants grown in controlled growth rooms for fertile and sterile conditions. We found that only the ORMDL gene (LOC_Os07g26940) showed differential expression under these conditions. To better understand the function of rice ORMDL genes, we generated RNAi transgenic rice plants suppressing either LOC_Os07g26940, or all three ORMDL genes present in rice. We found that the RNAi transgenic plants with low expression of either LOC_Os07g26940 alone or all three ORMDL genes were sterile, having abnormal pollen morphology and staining. In addition, we found that both sphingolipid metabolism and expression of genes involved in sphingolipid synthesis were perturbed in the tms2 mutant, analogous to the role of ORMs in yeast. Our results indicated that plant ORMDL proteins influence sphingolipid homeostasis, and deletion of this gene affected fertility resulting from abnormal pollen development.
血清类粘蛋白（ORM）是由ORM和ORMDL（类ORM）基因编码的内质网驻留多肽。在人类中，ORMDL3被报道为与哮喘相关的遗传风险因素。在酵母中，ORM蛋白作为鞘脂合成的负调节因子。鞘脂是调节包括应激反应和细胞凋亡在内的多个过程的重要分子。然而，ORM/ORMDL基因在植物中的功能尚未见报道。此前，我们发现由tms2控制的温敏型遗传雄性不育（TGMS）水稻品系在7号染色体上有一个约70 kb的缺失。我们鉴定出在穗中表达的四个基因，包括一个ORMDL直系同源基因，作为tms2的候选基因。在本报告中，我们对在可控生长室中生长的野生型植物在可育和不育条件下花药中正常表达的仅两个候选基因的表达进行了定量。我们发现，只有ORMDL基因（LOC_Os07g26940）在这些条件下表现出差异表达。为了更好地理解水稻ORMDL基因的功能，我们构建了抑制水稻中LOC_Os07g26940或所有三个ORMDL基因的RNAi转基因水稻植株。我们发现，单独低表达LOC_Os07g26940或所有三个ORMDL基因的RNAi转基因植株是不育的，花粉形态和染色异常。此外，我们发现tms2突变体中鞘脂代谢和参与鞘脂合成的基因表达均受到干扰，这与酵母中ORM的作用类似。我们的结果表明，植物ORMDL蛋白影响鞘脂稳态，该基因的缺失影响了花粉发育异常导致的育性。
