中国农业科学 ›› 2019, Vol. 52 ›› Issue (5): 786-800.doi: 10.3864/j.issn.0578-1752.2019.05.002

• 作物遗传育种·种质资源·分子遗传学 • 上一篇    下一篇

赤霉素GA4是水稻矮化特征的重要调节因子

黄升财1,王冰1,谢国强2,刘中来2,张美娟1,张树清1(),程宪国1()   

  1. 1 中国农业科学院农业资源与农业区划研究所,北京 100081
    2 九江农业科学院,江西九江 332101
  • 收稿日期:2018-11-06 接受日期:2018-12-09 出版日期:2019-03-01 发布日期:2019-03-12
  • 通讯作者: 张树清,程宪国
  • 作者简介:黄升财,E-mail: huangshengcai_123@163.com
  • 基金资助:
    转基因重大专项(2016ZX08010005-9)

Enrichment Profile of GA4 is an Important Regulatory Factor Triggering Rice Dwarf

HUANG ShengCai1,WANG Bing1,XIE GuoQiang2,LIU ZhongLai2,ZHANG MeiJuan1,ZHANG ShuQing1(),CHENG XianGuo1()   

  1. 1 Intitute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081
    2 Jiu Jiang Academy of Agricultural Sciences, Jiujiang 332101, Jiangxi
  • Received:2018-11-06 Accepted:2018-12-09 Online:2019-03-01 Published:2019-03-12
  • Contact: ShuQing ZHANG,XianGuo CHENG

摘要:

【目的】 以水稻幼胚组培过程中获得的一株半矮化水稻突变体为研究对象,解析水稻半矮化突变体株高变矮及分蘖增多等表型异常的原因,为克服水稻过度矮化发育障碍因子及培育抗倒伏高产水稻品种提供科学理论依据。【方法】 首先统计分析半矮化水稻突变体与野生型的表型差异,利用体式显微镜和光学显微镜观察突变体花的结构及其细胞特征;通过转录组测序及qRT-PCR分析差异基因的表达特征,并通过外源喷施赤霉素GA3处理检测突变体对外源赤霉素的敏感性;最后利用高效液相色谱和质谱联仪检测突变体内赤霉素的含量与富集特征。【结果】 表型观测与统计结果表明,突变体水稻株高比野生型减少56.59%,有效分蘖数高出47.44%,差异均达到极显著水平。突变体的表皮毛消失且花发育迟缓,雄蕊变小。尽管突变体分蘖数较高但结实率明显降低,仅为野生型的12.62%,且种子长度和宽度均减小,差异极显著。通过显微镜观察茎的纵切切片,发现突变体细胞长度减少23%,差异极显著。外源喷施赤霉素后突变体的株高、有效分蘖、结实率、种子大小、表皮毛和茎秆细胞长度均有不同程度的恢复,说明植物体内赤霉素合成不足可能是引起水稻矮化的主要原因。转录组测序结果显示突变体中OsGA13ox 显著上调,qRT-PCR验证结果与转录组测序结果一致。由于OsGA13ox控制GA12转化为GA53,而GA12和GA53分别转化为GA4和GA1,GA4的活性高于GA1,因此,突变体中GA4减少可能是导致半矮化的主要原因。赤霉素检测结果表明突变体中GA4含量减少94.9%,与预测结果一致。此外,D14作为SL(独脚金内酯)的特异性受体,参与调控植物SL信号转导,抑制枝条分枝或者分蘖。qRT-PCR结果显示,与野生型相比,突变体中D14 显著下调,而经过GA3处理的野生型和突变体中D14 均显著上调。D14 上调可能导致有效分蘖数减少,而其下调可能致使有效分蘖数增加。统计结果表明突变体中有效分蘖显著增多,而经过GA处理之后,野生型和突变体有效分蘖数均显著低于未经GA3处理前,表明D14 在水稻中的表达可能受到GA的调控从而影响水稻分蘖。【结论】 OsGA13ox 异常表达导致活性更高的GA4在水稻中的富集减少,形成水稻半矮化突变体;赤霉素可能通过影响D14 的表达间接调控水稻的分蘖。

关键词: 水稻, 半矮化突变体, OsGA13ox, 赤霉素GA4, D14, 有效分蘖

Abstract:

【Objective】A dwarf rice mutant was generated by culturing rice embryo tissues and characterized to elucidate the reasons for leading to an occurence of semi-dwarf rice with more tiller number. It is expected that this study will provide a theoretical basis for scientifically cultivating rice varieties of lodging-resistant and high-yielding in overcoming the dwarf obstacle factors.【Method】In this study, both the rice dwarf mutant and wild type were phenotypically profiled, and the structural characteristics of flower and cell appearance of leaves were investigated by stereomicroscope and light microscopy; The differential gene expression profiles were analyzed by both the transcriptomics and qRT-PCR, and the sensitivity of the mutant to exogenous gibberellin was detected by spraying exogenous GA3; The enrichment profiles of gibberellin in the mutant were detected by a high performance liquid chromatography and a mass spectrometry. 【Result】Data showed that the mutant demonstrated a decrease of 56.59% in the average plant height and an increase of 47.44% in the effective tiller number compared with the wild type, respectively (P <0.01). Observation showed that the mutant led to disappearance of the epidermis and revealed a smaller stamen accompanying a delayed development in the flower organs. Although the mutant has a higher effective tiller number, but significantly lowers the seed setting rate, which only accounts for 12.62% of that in the wild type. The length and the width of grains also are significantly reduced (P <0.01). Stem longitudinal sections reveal that the mutant decreased the cell length of 23% compared with the wild type (P <0.01). However, when the mutant was exposed to exogenous gibberellin, the plant height, effective tiller number, seed setting rate, seed size, epidermis and the stem cell length were obviously restored, indicating that the dwarf mutant possibly results from the shortage of GA’s synthesis in plant. Transcriptome sequencing showed that the mutant significantly up-regulated the OsGA13ox gene, and exhibited an identical result with the qRT-PCR analyses. Since the OsGA13ox controls the conversion of the GA12 to the GA53, both of which are converted to the GA4 and the GA1, respectively. Particularly, the GA4 exhibits a higher activity than the GA1, suggesting that rice dwarf might be triggered by the reduction of GA4 enrichment in plant. Measurement confirmed that the accumulation of the GA4 in the mutant was decreased by 94.9% compared with the wild type. Additionally, as a specific receptor for SL (Strigolactone), the D14 gene is involved in the SL signaling transduction in plant, and thus inhibits branching or tillering. The qRT-PCR showed that the mutant significantly down-regulated the D14 gene compared to the wild type, however, both the wild type and the mutant significantly up-regulated after spraying GA3. The data suggested that the up-regulation of the D14 gene might lower the effective tiller number, while the down-regulation of the D14 gene possibly increase the effective tiller number. Statistical analyses demonstrates that the mutant significantly increased the effective tiller number, but both the wild type and mutant decreased the effective tiller number after spraying GA3, indicating that the expression profiles of the D14 gene in rice might be modulated by GA, and thereby exert on the tiller number.【Conclusion】Semi-dwarfed rice mutant is likely caused by a decrease of GA4 enrichment because of abnormal expression of the OsGA13ox gene, and GA might indirectly regulate rice tiller by affecting the expression of the D14 gene.

Key words: rice, semi-dwarf mutant, OsGA13ox, GA4, D14, effective tiller