State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China; Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops, Ministry of Agriculture, Institute of Vegetables and Flowers, Chinese Academy of Agricultural Sciences, Beijing, 100081, China.
State Key Laboratory of Crop Genetics and Germplasm Enhancement, Key Laboratory of Biology and Germplasm Enhancement of Horticultural Crops in East China, Ministry of Agriculture, Nanjing Agricultural University, Nanjing, 210095, China.
Plant Sci. 2019 Mar;280:110-119. doi: 10.1016/j.plantsci.2018.10.027. Epub 2018 Nov 3.
The Brassica rapa (B. rapa) species displays enormous phenotypic diversity, with leafy vegetables, storage root vegetables and oil crops. These different crops all have different flowering time, which determine their growing season and cultivation area. Little is known about the effects of diverse temperature and day-lengths on flowering time QTL associated with FLC paralogues. We phenotyped the flowering time of a doubled haploid population, established from a cross between Yellow sarson and Pak choi under diverse environmental conditions. We identified flowering-time QTL (fQTL) in different photoperiod and temperature regimes in the greenhouse, and studied their colocation with known flowering time genes. As several fQTL colocalized with FLC paralogues, we studied the expression patterns of four FLC paralogues during the course of vernalization in parental lines. Under all environmental conditions tested the major fQTL that mapped to the BrFLC2_A02 locus was detected, however its effect decreased when plants were grown at low temperatures. Another fQTL that mapped to the FLC paralogue, BrFLC5_A03 was also identified under all tested environments, while no fQTL colocated with BrFLC1_A10 or BrFLC3_A03. Furthermore, the vernalization treatment decreased expression of all BrFLC paralogues in the parental lines, and showed the lowest transcript level after 28 days of vernalization. Transcript abundance stayed low after returning the plants for seven days to normal growth temperature. Interestingly, transcript abundance of BrFLC3_A03 and BrFLC5_A03 was repressed much stronger and already reached lowest levels after 14d in the early-flowering type YS-143. This study improves understanding of the effects of daylength and vernalization on flowering time in B. rapa and the role of the different BrFLC paralogues therein.
芸薹属（ Brassica rapa ）物种表现出巨大的表型多样性，包括绿叶蔬菜、块根蔬菜和油料作物。这些不同的作物具有不同的开花时间，这决定了它们的生长季节和种植区域。关于不同温度和日照长度对与 FLC 同源物相关的开花时间数量性状位点（QTL）的影响知之甚少。我们对来自黄籽薹和白菜杂交的加倍单倍体群体在不同环境条件下的开花时间进行了表型分析。我们在温室中不同光周期和温度条件下鉴定了开花时间 QTL（fQTL），并研究了它们与已知开花时间基因的共定位。由于几个 fQTL 与 FLC 同源物共定位，我们研究了在亲本系中春化过程中四个 FLC 同源物的表达模式。在所测试的所有环境条件下，主要的 fQTL 都映射到 BrFLC2_A02 位点，但当植物在低温下生长时，其效应降低。在所有测试的环境下，还鉴定到另一个映射到 FLC 同源物 BrFLC5_A03 的 fQTL，而没有与 BrFLC1_A10 或 BrFLC3_A03 共定位的 fQTL。此外，春化处理降低了亲本系中所有 BrFLC 同源物的表达水平，在春化 28 天后表现出最低的转录水平。将植物返回正常生长温度 7 天后，转录丰度仍然较低。有趣的是，BrFLC3_A03 和 BrFLC5_A03 的转录丰度受到更强的抑制，在早花型 YS-143 中，经过 14d 处理后已达到最低水平。本研究提高了对芸薹属中日照长度和春化对开花时间的影响以及不同 BrFLC 同源物在其中的作用的理解。
