Transcriptome analysis of exogenous auxin effect on lily underground stem bulbs formation

【Objective】To reveal the molecular mechanism of hormone regulation on the occurrence and development of lily underground stem bulbs,and to provide reference for further development of the molecular mechanism of auxin related genes regulation of lily underground stem bulbs.【Method】The underground stems of lily were treated with exogenous auxin indoleacetic acid(IAA)at concentrations of 0.2 and 2.0 mmol/L,and water treatment was used as the control(CK). The quantity and weight of harvested underground stem bulbs were measured. Combined with transcriptome sequencing analysis,the temporal and spatial expression patterns of various hormone-related genes under different auxin concentrations were revealed. Real-time fluorescence quantitative PCR was used to detect the expression level of key genes in lily lateral organogenesis.【Result】The total number of stem bulbs,number of stem bulbs per plant and average gram weight of stem bulbs of lily plants treated with 2.0 mmol/L concentration IAA were lower than those treated with 0.2 mmol/L concentration auxin and control group. The results of KEEG enrichment pointed to the plant hormone signal transduction pathway. The digital expression profiles of differentially expressed genes(DEGs)showed that almost all genes related to plant hormones were affected,including auxin,ethylene,ababolic acid,brassinolide,methyl jasmonate,cytokinin and gibberellin,among which methyl jasmonate had the most DEGs,followed by auxin. Real-time fluorescence quantitative PCR detection showed that the expression levels of WOX9,WOX11,KNOX2,CYCD3 and CYCD5 genes in 2.0 mmol/L treatment were significantly lower than those in CK(P<0.05).【Conclusion】High concentration of auxin IAA can effectively delay the formation and development of underground stem bulbs of lily. Exogenous auxin treatment not only affects the anabolism,transport and signal transduction of many plant hormones,but also inhibits the expression of key genes of lily lateral organogenesis,thus affecting the formation and development of underground stem bulbs.