Sajjad Muhammad, Ma Xiaoling, Habibullah Khan Sultan, Shoaib Muhammad, Song Yanhong, Yang Wenlong, Zhang Aimin, Liu Dongcheng
State Key Laboratory of Plant Cell and Chromosome Engineering, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, 1 West Beichen Road, Chaoyang District, Beijing, 100101, China.
Department of Environmental Sciences, COMSATS Institute of Information Technology, Vehari, 61100, Pakistan.
BMC Plant Biol. 2017 Oct 16;17(1):164. doi: 10.1186/s12870-017-1114-3.
The Flo2 gene is a member of a conserved gene family in plants. This gene has been found to be related to thousand grain weight (TGW) in rice. Its orthologs in hexaploid wheat were cloned, and the haplotype variation in TaFlo2-A1 was tested for association with TGW.
The cloned sequences of TaFlo2-A1, TaFlo2-B1 and TaFlo2-D1 contained 23, 23 and 24 exons, respectively. The deduced proteins of TaFlo2-A1 (1734 aa), TaFlo2-B1 (1698 aa) and TaFlo2-D1 (1682 aa) were highly similar (>94%) and exhibited >77% similarity with the rice FLO2 protein. Like the rice FLO2 protein, four tetratricopeptide repeat (TPR) motifs were observed in the deduced TaFLO2 protein. An 8-bp InDel (-10 to -17 bp) in the promoter region and five SNPs in first intron of TaFlo2-A1 together formed two haplotypes, TaFlo2-A1a and TaFlo2-A1b, in bread wheat. TaFlo2 was located on homeologous group 2 chromosomes. TaFlo2-A1 was inferred to be located on deletion bin '2AL1-0.85-1.00'. The TaFlo2-A1 haplotypes were characterized in the Chinese Micro Core Collection (MCC) and Pakistani wheat collection using the molecular marker TaFlo2-Indel8. TaFlo2-A1 was found to be associated with TGW but not with grain number per spike (GpS) in both the MCC and Pakistani wheat collections. The frequency of TaFlo2-A1b (positive haplotype) was low in commercial wheat cultivars; thus this haplotype can be selected to improve grain weight without negatively affecting GpS. The expression level of TaFlo2-A1 in developing grains at 5 DAF (days after flowering) was positively correlated with TGW in cultivars carrying the positive haplotype.
This study will likely lead to additional investigations to understand the regulatory mechanism of the Flo2 gene in hexaploid wheat. Furthermore, the newly developed molecular marker 'TaFlo2-InDel8' could be incorporated into the kit of wheat breeders for use in marker-assisted selection.
Flo2基因是植物中一个保守基因家族的成员。已发现该基因与水稻的千粒重（TGW）有关。克隆了其在六倍体小麦中的直系同源基因，并检测了TaFlo2 - A1的单倍型变异与千粒重的关联。
TaFlo2 - A1、TaFlo2 - B1和TaFlo2 - D1的克隆序列分别包含23、23和24个外显子。TaFlo2 - A1（1734个氨基酸）、TaFlo2 - B1（1698个氨基酸）和TaFlo2 - D1（1682个氨基酸）推导的蛋白质高度相似（>94%），且与水稻FLO2蛋白的相似度>77%。与水稻FLO2蛋白一样，在推导的TaFLO2蛋白中观察到四个四肽重复（TPR）基序。TaFlo2 - A1启动子区域的一个8碱基插入缺失（-10至-17 bp）和第一个内含子中的五个单核苷酸多态性（SNP）共同在面包小麦中形成了两个单倍型，TaFlo2 - A1a和TaFlo2 - A1b。TaFlo2位于2号同源群染色体上。推断TaFlo2 - A1位于缺失区间“2AL1 - 0.85 - 1.00”。利用分子标记TaFlo2 - Indel8对中国微核心种质库（MCC）和巴基斯坦小麦种质中的TaFlo2 - A1单倍型进行了鉴定。在MCC和巴基斯坦小麦种质中均发现TaFlo2 - A1与千粒重相关，但与每穗粒数（GpS）无关。TaFlo2 - A1b（正向单倍型）在商业小麦品种中的频率较低；因此，可以选择该单倍型来提高粒重，而不会对GpS产生负面影响。在开花后5天（DAF）发育籽粒中，TaFlo2 - A1的表达水平与携带正向单倍型品种的千粒重呈正相关。
本研究可能会引发更多研究，以了解六倍体小麦中Flo2基因的调控机制。此外，新开发的分子标记“TaFlo2 - Indel8”可纳入小麦育种者的工具包中，用于标记辅助选择。
