Yu Li, Ma Tengfei, Zhang Yuqin, Hu Ying, Yu Ke, Chen Yueyue, Ma Haoli, Zhao Jie
State Key Laboratory of Hybrid Rice, College of Life Sciences, Wuhan University, Wuhan, 430072, China.
BMC Plant Biol. 2017 Mar 7;17(1):60. doi: 10.1186/s12870-017-1004-8.
In rice, the pistil is the female reproductive organ, and it consists of two stigmas and an ovary. The stigma is capable of receiving pollen grains and guiding pollen tube growth. The ovary holds the embryo sac, which is fertilized with male gametes to produce seed. However, little is known about the gene function and regulatory networks during these processes in rice.
Here, using the RNA-Seq technique, we identified 3531 stigma-preferential genes and 703 stigma-specific genes within the rice pistils, and we verified 13 stigma-specific genes via qRT-PCR and in situ hybridization. The GO analysis showed that the transport-, localization-, membrane-, communication-, and pollination-related genes were significantly enriched in the stigma. Additionally, to identify the embryo sac-preferential/specific genes within the pistils, we compared a wild-type ovary with a mutant dst (defective stigma) ovary and found that 385 genes were down-regulated in dst. Among these genes, 122 exhibited an ovary-specific expression pattern and are thought to be embryo sac-preferential/specific genes within the pistils. Most of them were preferentially expressed, while 14 of them were specifically expressed in the pistil. Moreover, the rice homologs of some Arabidopsis embryo sac-specific genes, which played essential roles during sexual reproduction, were down-regulated in dst. Additionally, we identified 102 novel protein-coding genes, and 6 of them exhibited differences between the stigma and ovary in rice as determined using RT-PCR.
According to these rice ovary comparisons, numerous genes were preferentially or specifically expressed in the stigma, suggesting that they were involved in stigma development or pollination. The GO analysis indicated that a dry rice stigma might primarily perform its function through the cell membrane, which was different from the wet stigma of other species. Moreover, many embryo sac-preferential/specific genes within the pistils were identified and may be expressed in female rice gametophytes, implying that these genes might participate in the process of female gametophyte specialization and fertilization. Therefore, we provide the gene information for investigating the gene function and regulatory networks during female gametophyte development and fertilization. In addition, these novel genes are valuable for the supplementation and perfection of the existing transcriptome in rice, which provides an effective method of detecting novel rice genes.
在水稻中，雌蕊是雌性生殖器官，由两个柱头和一个子房组成。柱头能够接收花粉粒并引导花粉管生长。子房容纳胚囊，胚囊与雄配子受精产生种子。然而，关于水稻这些过程中的基因功能和调控网络知之甚少。
在此，我们使用RNA测序技术，在水稻雌蕊中鉴定出3531个柱头优先表达基因和703个柱头特异性基因，并通过qRT-PCR和原位杂交验证了13个柱头特异性基因。基因本体（GO）分析表明，与运输、定位、膜、通讯和授粉相关的基因在柱头中显著富集。此外，为了鉴定雌蕊中的胚囊优先表达/特异性基因，我们将野生型子房与突变体dst（缺陷柱头）子房进行比较，发现dst中有385个基因下调。在这些基因中，122个表现出子房特异性表达模式，被认为是雌蕊中的胚囊优先表达/特异性基因。它们中的大多数是优先表达的，而其中14个在雌蕊中特异性表达。此外，一些在有性生殖过程中起重要作用的拟南芥胚囊特异性基因的水稻同源物在dst中下调。此外，我们鉴定出102个新的蛋白质编码基因，其中6个在水稻柱头和子房中表现出差异，这是通过RT-PCR确定的。
根据这些水稻子房的比较，许多基因在柱头中优先或特异性表达，表明它们参与柱头发育或授粉。GO分析表明，水稻的干燥柱头可能主要通过细胞膜发挥其功能，这与其他物种的湿润柱头不同。此外，在雌蕊中鉴定出许多胚囊优先表达/特异性基因，它们可能在水稻雌配子体中表达，这意味着这些基因可能参与雌配子体特化和受精过程。因此，我们提供了用于研究雌配子体发育和受精过程中基因功能和调控网络的基因信息。此外，这些新基因对于补充和完善水稻现有的转录组很有价值，这提供了一种检测水稻新基因的有效方法。
