Comparative transcriptome analysis provides novel insights into phytohormone dynamic changes during seed germination in carrot (Daucus carota L.)

The germination of carrot seeds is a complex regulatory process and the relationship between phytohormone and carrot seed germination is unclear. We performed morphological observation, transcriptome sequencing, phytohormone content determination, and gene expression profiles analysis. The results showed that the white hypocotyls of carrot seeds grew rapidly on the 3 d, and cotyledons unfold on the 8 d. A total of 745 differentially expressed genes (DEGs) related to plant hormone signal transduction were identified at different germination stages (3, 5, 8 d), and most of the genes were up-regulated obviously in the later stage. The content of GA3 reached its peak on the first day of germination, with a content of 7.12 ng/g FW, and showed a trend of first decreasing, then increasing and decreasing. And the trend of GA4 content change was similar to GA3 content from 2 d to 8 d. The contents of indole-3-acetic acid (IAA) and methyl jasmonate (MeJA) showed a gradual increasing trend, while the content of abscisic acid (ABA) gradually decreased. The results of RT-qPCR showed that DcGA3ox1 and DcAOC expressed decreased, while DcGA20ox2 and DcYUCCA increased in the whole process. These results provide potential new insights for the efficient production of carrots..

胡萝卜种子的萌发是一个复杂的调控过程，植物激素与胡萝卜种子萌发之间的关联尚不明确。本研究开展了形态学观察、转录组测序、植物激素含量测定以及基因表达谱分析。结果显示，胡萝卜种子的白色下胚轴于萌发第3天快速生长，子叶于第8天展开。在不同萌发阶段（3、5、8天）共鉴定出745个与植物激素信号转导相关的差异表达基因（DEGs），其中多数基因在萌发后期显著上调。赤霉素3（GA3）在萌发首日达到含量峰值，为7.12 ng/g 鲜重（FW），并呈现先下降、后上升再下降的变化趋势。赤霉素4（GA4）在2至8天的含量变化趋势与GA3相似。吲哚-3-乙酸（indole-3-acetic acid, IAA）与茉莉酸甲酯（methyl jasmonate, MeJA）的含量均呈逐渐上升趋势，而脱落酸（abscisic acid, ABA）的含量则逐步下降。实时荧光定量PCR（RT-qPCR）结果显示，DcGA3ox1与DcAOC的表达量在整个萌发过程中均下调，而DcGA20ox2与DcYUCCA的表达量则上调。上述研究结果为胡萝卜的高效生产提供了潜在的全新研究视角。