The APETALA2-like transcription factor SUPERNUMERARY BRACT controls rice seed shattering and seed size

First author: Liyun Jiang; Affiliations: China Agricultural University (中国农业大学): Beijing, China

Corresponding author: Lubin Tan

The elimination of seed shattering was a crucial event during crop domestication. Improving and fine-tuning the regulation of this process will further enhance grain yield by avoiding seed losses during crop production. In this work, we identified a loss-of-shattering mutant suppression of shattering 1 (ssh1) through a screen of mutagenized wild rice introgression lines with naturally high shattering. Using the MutMap approach and transformation experiments, we isolated a genetic factor for seed shattering, SSH1, which is an allele of SUPERNUMERARY BRACT (SNB), a gene encoding a plant-specific APETALA2-like transcription factor. A C-to-A point mutation in the 9th intron of SNB altered the splicing of its mRNA, causing the reduced shattering of the ssh1 mutant by altering the development of the abscission layer and vascular bundle at the junction between the seed and the pedicel. Our data suggest that SNB positively regulates the expression of two rice REPLUMLESS (RPL) homologs, qSH1 and SH5. In addition, the ssh1 mutant had larger seeds and a higher grain weight, resulting from its increased elongation of the glume longitudinal cells. The further identification of favorable SNB alleles will be valuable for improving rice seed shattering and grain yield using molecular breeding strategies.

种子落粒性的消失是作物驯化过程中的一个重要事件。该过程的改良和精细调控将会通过在作物生产过程中避免不必要的种子损失来进一步的增加籽粒产量。本文中，作者通过诱变的野生水稻导入系群体鉴定到了一个落粒性丢失突变体ssh1。通过MutMap的方法和遗传转化实验，作者分离出了一个控制籽粒脱落的遗传因子SSH1，该基因是SNB的一个等位基因，SNB基因编码了一个植物特异性类APETALA2转录因子。SNB基因第九个内含子C-to-A的点突变会改变该基因mRNA的可变剪切，并通过改变种子和花梗之间连接处离层和维管束的发育降低ssh1突变体中的种子落粒性。本文的数据显示SNB基因正向调控两个水稻RPL同源基因qSH1和SH5的表达。另外，ssh1突变体由于颖片纵向细胞伸长增加，而导致种子更大，籽粒重量更高。对于SNB等位基因进一步的研究分析将有助于未来通过分子育种策略对水稻种子落粒性和籽粒产量作进一步的改良。

通讯：谭禄宾 (http://cab.cau.edu.cn/art/2017/6/9/art_27217_76.html)

个人简介：1996-2000年，湖南农业大学，学士；2001-2004年，中国农业大学，硕士；2004-2007年，中国农业大学，博士；2007-2010年，清华大学生命科学学院，博士后；2013-2014年，美国佛罗里达大学农学系，访问学者；2010-至今，中国农业大学植物遗传育种系，副教授/博导。

研究方向：水稻重要农艺性状遗传调控网络解析。

doi: https://doi.org/10.1105/tpc.18.00304

Journal: Plant Cell

First Published: 09 January, 2019