Cai Huilin, Chen Yulong, Zhang Min, Cai Ronghao, Cheng Beijiu, Ma Qing, Zhao Yang
National Engineering Laboratory of Crop Stress Resistance/Key Laboratory of Crop Biology of Anhui Province, School of Life Sciences, Anhui Agricultural University, Hefei, 230036 China.
Physiol Mol Biol Plants. 2017 Jan;23(1):143-154. doi: 10.1007/s12298-016-0404-9. Epub 2016 Dec 21.
Starch occupies the maximal component of cereal grains and is pivotal for maize yield and quality. However, the regulatory mechanism of starch synthesis is still poorly understand. In this study, a GRAS transcription factor, , was isolated from maize inbred line B73 based on transcriptome sequencing. Quantitative real-time PCR indicated that is specifically expressed in maize endosperm. Transient expression of ZmGRAS20-green fluorescent protein fusion protein in tobacco cells showed a nucleus and membrane localization of the protein. Transactivation assay of ZmGRAS20 demonstrated that it has no transactivation activity in yeast cells. Overexpression of led to a chalky region of ventral endosperm with decreased starch content and defective agronomic characters in transgenic seeds. Moreover, -overexpression plants had fewer fractions of long-branched starch chains. Further scanning electron microscopy observation of transgenic seeds exhibited altered starch granules morphology compared with wide type plants. Taken together, these results suggested that may function as a starch synthesis regulatory factor in rice endosperm.
淀粉是谷物籽粒中的主要成分，对玉米产量和品质至关重要。然而，淀粉合成的调控机制仍不清楚。本研究基于转录组测序从玉米自交系B73中分离出一个GRAS转录因子。实时定量PCR表明该基因在玉米胚乳中特异性表达。ZmGRAS20-绿色荧光蛋白融合蛋白在烟草细胞中的瞬时表达显示该蛋白定位于细胞核和细胞膜。ZmGRAS20的反式激活分析表明它在酵母细胞中没有反式激活活性。该基因的过表达导致转基因种子胚乳腹侧出现垩白区域，淀粉含量降低，农艺性状不良。此外，过表达植株中长支链淀粉链的比例较低。进一步对转基因种子进行扫描电子显微镜观察，发现与野生型植株相比，淀粉粒形态发生了改变。综上所述，这些结果表明该基因可能作为水稻胚乳中的淀粉合成调控因子发挥作用。
