Transcriptomic Analysis Of Flower Bud Differentiation In Ornamental Pineapple

Ornamental pineapple is a trendy flower with both foliage and flowers.It is deeply loved by people for its diverse varieties,beautiful plant types,gorgeous flowers and long viewing period,and has become a potted flower that has swept the Chinese market.Because its natural flowering time is long and irregular,it usually uses flower-promoting agents in production to achieve regular flowering.At present,the best flower-promoting effect is the saturated aqueous solution of acetylene,but how does acetylene regulate the flowering of ornamental pineapples? And what is the molecular mechanism that causes plants to bloom after acetylene treatment? These issues need to be studied.This study uses the "starlight" from Guzmania Ruiz & Pay as the material,through comparative transcriptomics analysis,bioinformatics analysis,expression pattern analysis,changes in endogenous hormone ACC(1-aminocyclopropane-1-carboxylic acid)content,and total soluble sugar content To study the mechanism of acetylene-induced flowering of ornamental pineapples from both molecular and physiological aspects.The main findings are as follows:(1)The results of comparative transcriptomics analysis showed that a total of 3291 differentially expressed gene fragments were obtained in the stem tips of ornamental pineapples after acetylene inducing flowers.Among them,there were 2256down-regulated gene fragments and 1035 up-regulated gene fragments;8 gene fragments were selected for this The q RT-PCR(Real-time Quantitative Polymerase Chain Reaction),q RT-PCR results are consistent with the sequencing results,indicating that the transcriptome sequencing results are true and credible.(2)Among the 3291 differentially expressed gene fragments screened,873 differentially expressed gene fragments were annotated into 109 pathways in the KEGG database,of which 16 pathways were significantly enriched,including phenylpropanol biosynthetic pathways,Phenylpropane biosynthesis pathway,starch sucrose metabolism pathway,flavonoid biosynthesis pathway and other pathways,these pathways may be related to the conversion of ornamental pineapple vegetative growth to reproductive growth,flower bud differentiation and energy metabolism.8 differentially expressed gene fragments related to ethylene biosynthesis were obtained by further screening.Among them,one ACC synthase gene ACS(ACC synthase gene)was up-regulated.It is speculated that it may be related to the synthesis of ACC and the increase of ethylene content in the flower bud when acetylene induces the flower bud differentiation of ornamental pineapple.(3)Based on the two cloned genes Ac FT and Ac MYB in the laboratory,bioinformatics analysis and expression pattern analysis of these two genes were carried out.The results showed that Ac FT is a hydrophilic protein composed of 175 amino acids and belongs to the PEBP superfamily;Ac FT is almost not expressed in roots and leaves,only expressed in buds,and the expression level after stimulating flowering is significantly higher than that of not stimulating flowering;The expression of Ac FT in different periods after urging flowers showed a trend of first rising,then falling and then rising.The increase in the expression level about 11 days after the initiation of flowering may be due to the acetylene starting to induce the differentiation of flower buds,Subsequently,the expression level increased again about 28 days after urging the flower,which may be related to the differentiation of flower buds and the formation of flower organs.Ac MYB is a hydrophilic protein composed of 374 amino acids and belongs to the SANT superfamily.It contains highly conserved R2 and R3 domains,so it belongs to the R2R3-MYB transcription factor;Ac MYB is almost not expressed in roots,and its expression in buds and leaves after stimulating flowering is significantly lower than that in the control group;Except for the increase in the 5 days after the urging,the expression of Ac MYB decreased significantly in each subsequent period after urging flowers.It is speculated that this gene may play a role in the early stage of flower bud differentiation.(4)Acetylene can promote the flowering of ornamental pineapples,while silver nitrate(ethylene synthesis inhibitor)can inhibit the flower-promoting effect of acetylene.It is speculated that acetylene may regulate flower bud differentiation through the ethylene signal pathway.Acetylene can also promote the increase in the ACC content of the ethylene synthesis precursor in the ornamental pineapple flower buds,while silver nitrate significantly inhibits the increase in the ACC content caused by acetylene-induced flowering,which further shows that acetylene induces the flower formation of ornamental pineapples by promoting the synthesis of endogenous ethylene,that is,acetylene induces the flower formation of ornamental pineapples through the ethylene signal pathway.Acetylene can also promote the increase of total soluble sugar content in buds,while silver nitrate treatment leads to a decrease in total soluble sugar content.It is speculated that the increase in soluble sugar content can provide energy for the differentiation of flower buds,thereby promoting the flowering of ornamental pineapples.