Effects of calcium application rate on the growth and calcium transport key gene family ACA expression in Chinese cabbage

【Abstract】To explore the effects of calcium application rate on expression of the key gene family ACA of growth and calcium transport in Chinese cabbage, and to study the molecular regulation mechanism of calcium absorption, transport and enrichment in cabbage, which could provide theoretical basis for further breeding of new calcium-rich Chinese cabbage and the rational application of calcium fertilizer in cultivation. 【Method】A pot experiment was conducted on 2 varieties of Chinese cabbage, Heiyewuyueman and Shanghailiuyueman, with 0, 0.2, 0.4, 0.6 and 0.8 g/kg calcium application rates to determine aboveground and root biomass, calcium content and calcium accumulation of Chinese cabbage, and 0 g/kg was as control. Control and 0.8 g/kg Chinese cabbage leaves were selected for transcriptome sequencing, differential expression genes（DEGs） were screened, GO function annotation and KEGG signaling pathway enrichment analysis were performed, and the effects of calcium application on ACA gene family expression were verified by real-time fluorescence quantitative PCR. 【Result】With the increase of calcium application rate, the aboveground dry weight, root dry weight and calcium content of Heiyewuyueman and Shanghailiuyueman increased first and then decreased, calcium content in shoots and roots of the 2 varieties reached the peak at 0.4 and 0.6 g/kg calcium application rates and were significantly higher than control（P＜0.05, the same below）. The above-ground calcium accumulation of the 2 varieties showed a trend of increasing first and then decreasing with the increase of calcium application rate. The accumulation of calcium in root system showed an increasing trend. There were 87 DEGs between 0.8 g/kg calcium application rate treatment and control in Heiyewuyueman, and 176 DEGs between 0.8 g/kg calcium application rate treatment and control in Shanghailiuyueman. DEGs was mainly annotated on GO function items such as cellular process, metabolic process, binding and catalytic activity. KEGG signaling pathways such as tyrosine metabolism, glucoside biosynthesis and plant hormone signaling transduction were significantly enriched. Twenty-five ACA gene family members were identified from DEGs. The results of real-time fluorescence quantitative PCR showed that the relative expression levels of ACA4-4 and ACA10-1 genes in 2 Chinese cabbage varieties treated with 0.6 and 0.8 g/kg calcium application rate were significantly up-regulated compared with the control, relative expression level of ACA11-2 gene in Heiyewuyueman treated with 0.6 g/kg calcium application rate was significantly up-regulated compared with the control. The correlation analysis between ACA gene expression and calcium content in Chinese cabbage showed that the relative expression levels of ACA4-4,ACA10-1 and ACA11-2 genes were positively correlated with calcium content in Chinese cabbage, and the relative expression levels of ACA4-4 genes were significantly correlated with calcium content in Chinese cabbage.【Conclusion】The dry weight and calcium content of aboveground and roots of Chinese cabbage are significantly increased by applying proper amount of calcium. Key calcium transport genes ACA4-4, ACA10-1 and ACA11-2 are screened, suggesting that ACA gene family members play an important role in calcium transport and accumulation in Chinese cabbage.