Miao Hongxia, Sun Peiguang, Liu Qing, Liu Juhua, Jia Caihong, Zhao Dongfang, Xu Biyu, Jin Zhiqiang
Key Laboratory of Tropical Crop Biotechnology, Ministry of Agriculture, Institute of Tropical Bioscience and Biotechnology, Chinese Academy of Tropical Agricultural Sciences, 571101 Haikou, People's Republic of China.
Key Laboratory of Genetic Improvement of Bananas, Haikou Experimental Station, Chinese Academy of Tropical Agricultural Sciences, 571101 Haikou, Hainan Province People's Republic of China.
Hortic Res. 2020 Jul 1;7:101. doi: 10.1038/s41438-020-0325-1. eCollection 2020.
Starch branching enzyme (SBE) has rarely been studied in common starchy banana fruits. For the first time, we report here the molecular characterization of seven () and six () genes in the banana A- and B-genomes, respectively, which could be classified into three distinct subfamilies according to genome-wide identification. Systematic transcriptomic analysis revealed that six s and six s were expressed in the developing banana fruits of two different genotypes, BaXi Jiao (BX, AAA) and Fen Jiao (FJ, AAB), among which and were highly expressed. Transient silencing of expression in banana fruit discs led to a significant decrease in its transcription, which coincides with significant reductions in total starch and amylopectin contents compared to those of empty vector controls. The suggested functional role of in banana fruit development was corroborated by its transient overexpression in banana fruit discs, which led to significant enhancements in total starch and amylopectin contents. A number of transcription factors, including three auxin response factors (ARF2/12/24) and two MYBs (MYB3/308), that interact with the promoter were identified by yeast one-hybrid library assays. Among these ARFs and MYBs, MaARF2/MaMYB308 and MaARF12/MaARF24/MaMYB3 were demonstrated via a luciferase reporter system to upregulate and downregulate the expression of , respectively.
淀粉分支酶（SBE）在普通淀粉质香蕉果实中鲜有研究。我们首次在此报告香蕉A基因组和B基因组中分别有7个（）和6个（）基因的分子特征，根据全基因组鉴定，这些基因可分为三个不同的亚家族。系统的转录组分析表明，6个和6个在两种不同基因型的香蕉果实发育过程中表达，即巴西蕉（BX，AAA）和粉蕉（FJ，AAB），其中和高度表达。在香蕉果实圆片中瞬时沉默的表达导致其转录显著下降，这与空载体对照相比，总淀粉和支链淀粉含量显著降低相吻合。在香蕉果实圆片中瞬时过表达，导致总淀粉和支链淀粉含量显著增加，从而证实了其在香蕉果实发育中的功能作用。通过酵母单杂交文库分析鉴定了许多与启动子相互作用的转录因子，包括三个生长素反应因子（ARF2/12/24）和两个MYB（MYB3/308）。在这些ARF和MYB中，通过荧光素酶报告系统证明MaARF2/MaMYB308和MaARF12/MaARF24/MaMYB3分别上调和下调的表达。
