赤霉素GA4＋7处理下白桦无性系生长及差异基因表达分析

Analysis of Clonal Growth and Differences in Gene Expression of Betula platyphylla × B. pendula under GA_(4+7)Treatment

[目的]为研究赤霉素GA4+7对白桦生长的调控机制。[方法]试验利用1个白桦无性系的分株材料,连续2年分别叶面喷施浓度为0.2 g·L^(-1)(T1)、0.4 g·L^(-1)(T2)的GA4+7溶液,对实验苗木的生长情况进行跟踪调查,并对相应顶端生长组织进行转录组测序和差异基因分析。[结果]对2个年份的苗高、地径等性状分析发现,不同处理间苗高与地径的差异均达到显著或极显著水平,GA4+7对高生长有明显的促进作用,2年后的T2白桦苗高较CK提高了19.65%。于6月28日取GA4+7连续处理2年的白桦顶芽开展RNA-seq分析,结果显示:0.4 g·L^(-1)GA4+7(T2)处理与对照(CK)间的差异基因数量最多,即上调表达的基因有181个,下调表达的基因有55个,这些差异基因在叶绿体类囊体膜、红光、远红光及蓝光的细胞响应等方面富集明显。Pathway富集分析显示:氧化磷酸化途径与光合途径中的8条基因呈上调表达,认为施加0.4 g·L^(-1)GA4+7处理后,上述基因的上调表达加快电子传递进程、催化ATP的合成,从而促进白桦光合作用增强,提高苗期生长量。[结论]对白桦外源施加赤霉素GA4+7后,可上调氧化磷酸化途径和光合途径相关基因的表达,进而促进苗木的高和地径生长。研究结果可为白桦生长相关途径基因的克隆提供参考。

[ Objective ] To explore the regulation mechanism of gibberellin GA4 ＋7 on the growth of birch. [ Method] The experiment was carried out by using two treatments from a tissue-cultured plantlet. The leaf surface was treated by foliar spraying GA4-7 solution with concentrations of 0.2 g ·L^-1（T1） and 0.4 g ·L^-1 （T2） for two consecutive years, respectively. Then the differential gene and transcriptome sequencing of the corresponding top growth tissue were analyzed. [ Result ] It was found that the difference of height and ground diameter of the plantlet under different treatments reached significant or extremely significant level after two years. It is proved that the GA4 ＋7 has a significant promoting effect on height growth. The height of birch seedlings under T2 treatment increased by 19.65% compared with the CK. The results of RNA-seq analysis of birch bud for treated by GA4＋7 for continuous 2 years showed that the number of different gene was the most between the 0.4 g·L^-1of GA4＋7 （T2） treatment and the CK, a total of 181 up-regulated expression genes and 55 down-regulated expression genes were observed. These genes presented significantly enrichment in the chloroplast thylakoid membrane, red light and far red light and blue light cell response. Pathway enrichment analysis showed that 8 genes in the oxidative phosphorylation pathway and photosynthetic pathway were up-regulated, indicating that applying on 0.4 g·L^-1GAg＋7 treatment, the up-regulated gene expression above promoted the electron transfer process, catalyzing ATP synthesis, thereby promoting birch photosynthetic enhancement, and improved seedling growth. [ Conclusion ] The application of exogenous gibberellin GA4.7 can upregulate the expression of related genes, which participates oxidative phosphorylation pathway and photosynthetic pathway, thus contributing to seedling height and diameter growth.