Metabolic Analysis Of Plant Hormones Related To Germination Of Sugarcane Axillary Buds And Screening Of Germination Inducer

Sugarcane is an important sugar crop in the world,which produces more than 80%of the world’s total sugar output.Sugarcane is an asexual perennial crop,which propagates by axillary buds on stem nodes.Production practice shows that axillary bud germinating is a key factor affecting seedling emergence,permanent root growth,effective stem number and sugarcane stalk yield.At present,studies on axillary bud germination in sugarcane mainly focus on the influence of external environmental factors and plant hormones on axillary bud germination,and the internal physiological and molecular mechanisms are still unclear,which limits the ability to improve sugarcane yield through axillary bud regulation.In view of this,this study tested the sugarcane axillary bud dormancy,stirring,swelled,elongation,the first new leaf in five stages such as plant endogenous hormones change and transcriptome differences in gene expression profile,revealing the sugarcane axillary bud physiological and molecular mechanism.Based on the results of of research to develop regulators that can promote the rapid germination of sugarcane axillary buds.The main results are as follows:1.Changes of endogenous hormone content in sugarcane during axillary bud germinationStudies on the changes of endogenous hormone content in sugarcane axillary buds from dormancy,germination,expansion,elongation,and the appearance of the first new leaf showed that gibberellin decreased in the germination stage,and then decreased in the expansion stage;auxin decreased gradually during the growth and development of sugarcane axillary buds.Gibberellin decreasedin the germination stage,and leveled off during the swelling period,and then decreased in the expression stage.Abscisic acid was down-regulated in the period of germination,up-regulated in the period of expansion,and down-regulated in the period of elongation.Ethylene in axillary bud growth and germination stage of sugarcane was up-regulated,then down regulated to elongation stage,then up regulated.Cytokinin was up-regulated during the germination of sugarcane axillary buds.The results showed that auxin and cytokinin played opposite roles in the whole process of sugarcane axillary bud development of,and other endogenous hormones may vary with different developmental stages.2.Transcriptome data analysis during the axillary bud germinating period of sugarcaneThe transcriptome differential gene expression profiles of axillary buds of ROC22,a major sugarcane cultivar in China,were constructed from five developmental stages:dormancy,germination,expansion,elongation and the appearance of the first new leaf.Plant hormones and nitrogen are closely related to the axillary bud germination of sugarcane.This study focuses on the analysis of the expression of genes in endogenous hormone signal transduction pathways and nitrogen cycle way.The results showed that auxin,gibberellin,cytokinin,abscisic acid and ethylene,the five signal transduction pathways have significant differential expression genes in different stages of axillary bud germination,among which in sugarcane axillary bud.During the germination stage,cytokinin signal transduction pathway genes play an up-regulated role.In the nitrogen cycle pathway,many genes with obvious differentially expressed were found also.Overall,compared with the dormant stage,there are 7345differentially expressed genes in the germination stage,of which 2807 are up-regulated and 4538 are down-regulated,auxin signal transduction pathway and cytokinin signal transduction pathway play important roles;compared with the germination stage,there are 55 differentially expressed genes in the expansion stage,of which 20 are up-regulated and 35 are down-regulated.The nitrogen metabolism pathway plays an important role;compared with the expansion stage,there are 6779 differentially expressed genes in the elongation stage,of which 3635 are up-regulated and 3144 are down-regulated.The nitrogen metabolism pathway and cytokinin signal transduction pathway play important roles;compared with the elongation stage,there are 4452 differentially expressed genes in the emergence of the first new leaf,of which 1100 are up-regulated and 3352 are down-regulated.The nitrogen metabolism pathway and auxin signal transduction pathway play important roles.Eleven differentially expressed genes were screened out for real-time quantitative PCR.The results showed that the trend was the same as transcriptome data,and their expression was indeed related to the sprouting of sugarcane axillary buds.3.Screening of inducers for promoting germinationAccording to the analysis of plant endogenous hormones and transcriptomics,plant cytokinin and nitrogen do play an important role in promoting the axillary bud germination of sugarcane.In order to develop a regulator to promote the sprouting of sugarcane axillary buds,different concentrations of exogenous cytokinin（6-BA）and nitrogen（NH₄NO₃）were applied to sugarcane axillary buds.The results showed that 50 mg/L6-BA+150 mg/L NH₄NO₃ and 100 mg/L 6-BA+150 mg/L NH₄NO₃could accelerate the process of axillary bud sprouting of sugarcane,with shorter time,faster growth and better effect than other treatments,which could be further tested and demonstrated,and could be used as plant regulator for promoting axillary bud sprouting in sugarcane production.