Promoter variation of MdSAUR14 modulates shoot elongation in spur-type apples
Xiuhua Gao, Lu Tong, Yandong Liu, Yiming Wang, Yu Liu, Muhammad Mobeen Tahir, Xiaoyun Zhang, Shun Du, Hanxiao Gao, Zhao Wan, Zhi Liu, Dongmei Wang, Jiangping Mao, Juanjuan Ma, Xiya Zuo, Dong ZhangAbstract
The application of spur-type varieties is crucial for achieving dwarfing and dense planting cultivation. However, the underlying mechanisms regulating the spur-type phenotype remain unclear. In this study, we created an F1 population by crossing ‘Hanfu’ (HF, spur-type) with ‘Wangxianghong’ (WXH, standard-type) and observed that the spur rate in F1 hybrid population followed a normal distribution. Though bulked segregant analysis (BSA) and RNA-sequencing analysis (RNA-seq), we identified 85 differentially expressed genes across three QTL regions were screened. Interestingly, small auxin-up RNA 14 (MdSAUR14) exhibited distinct expression patterns in ‘HF,’ ‘WXH,’ and their extreme hybrid populations, suggesting a close association between its expression levels and the spur-type phenotype. MdSAUR14-overexpressed apple lines exhibited greater plant height and increased average internode length compared to wild type (WT) plants. A double base substitutions (DBS) variation in the MdSAUR14 promoter is closely linked to the spur phenotype. Furthermore, the presence of the DBS impacts the binding ability of BRASSINAZOLE-RESISTANT 1 (MdBZR1), which subsequently influences MdSAUR14 activity. Our study elucidates DBS-related genetic variation and mechanisms underlying shoot elongation in spur-type varieties.