Tian Zhendong, Wu Bei, Liu Jing, Zhang Libo, Wu Ting, Wang Yi, Han Zhenhai, Zhang Xinzhong
College of Horticulture, China Agricultural University, Beijing, China.
College of Horticultural Science & Technology, Hebei Normal University of Science & Technology, Qinhuangdao, China.
Mol Breed. 2024 Jan 11;44(1):1. doi: 10.1007/s11032-024-01441-4. eCollection 2024 Jan.
Final fruit size of apple () cultivars is related to both mesocarp cell division and cell expansion during fruit growth, but it is unclear whether the cell division and/or cell enlargement determine most of the differences in fruit size between species. In this study, by using an interspecific hybrid population between "Zisai Pearl" and cultivar "Red Fuji," we found that the mesocarp cell number was the main causal factor of diversity in fruit size between species. Rapid increase in mesocarp cell number occurred prior to 28 days after anthesis (DAA), while cell size increased gradually after 28 DAA until fruit ripening. Six candidate genes related to auxin signaling or cell cycle were predicted by combining the RNA-seq data and previous QTL data for fruit weight. Two InDels and 10 SNPs in the promoter of a small auxin upregulated RNA gene in Zisai Pearl led to a lower promoter activity than that of Red Fuji. One non-synonymous SNP G/T at 379 bp downstream of the ATG codon of , which was heterozygous in Zisai Pearl, exerted significant genotype effects on fruit weight, length, and width. Transgenic apple calli by over-expressing or RNAi confirmed that participated in the negative regulation of mesocarp cell division and thus apple fruit size. These results could provide new insights in the molecular mechanism of small fruit size in accession and be potentially used in molecular assisted breeding via interspecific hybridization.
The online version contains supplementary material available at 10.1007/s11032-024-01441-4.
苹果（）品种的最终果实大小与果实生长期间的中果皮细胞分裂和细胞扩张均有关，但尚不清楚细胞分裂和/或细胞增大是否决定了不同品种间果实大小的大部分差异。在本研究中，通过利用“紫塞明珠”与“红富士”品种间的种间杂交群体，我们发现中果皮细胞数量是不同品种间果实大小差异的主要因果因素。中果皮细胞数量在开花后28天（DAA）之前迅速增加，而细胞大小在28 DAA之后逐渐增加直至果实成熟。通过结合RNA-seq数据和先前关于果实重量的QTL数据，预测了6个与生长素信号传导或细胞周期相关的候选基因。“紫塞明珠”中小生长素上调RNA基因启动子中的2个InDel和10个SNP导致其启动子活性低于“红富士”。位于起始密码子下游379 bp处的一个非同义SNP G/T在“紫塞明珠”中为杂合型，对果实重量、长度和宽度具有显著的基因型效应。通过过表达或RNA干扰的转基因苹果愈伤组织证实参与了中果皮细胞分裂的负调控，从而影响苹果果实大小。这些结果可为阐明“紫塞明珠”果实小的分子机制提供新见解，并有可能用于种间杂交的分子辅助育种。
在线版本包含可在10.1007/s11032-024-01441-4获取的补充材料。
