The Transcriptomics Study On The Effect Of Nitrogen Application On Fall Axillary Shoot Bud Formation In Leymus Chinensis

Leymus chinensis is a perennial rhizome grass,widely distributed in the eastern Eurasian grassland.In natural condition,it has a high economic value and ecological value.However,sexual reproduction ability is weak that limiting the establishment of L.chinensis artificial grassland.The low seed yield of L.chinensis is mainly related to the small number of reproductive shoots per unit area,which is closely related to the formation of underground axillary shoot buds during the post-fruit vegetative period in the fall.Therefore,exploring how the underground axillary shoot buds formating in the post-vegetative stage has become the crucial factor to explain the low seed yield in L.chinensis.In this study,the transcriptomics method was used to comparatively study the changes in gene expression and regulatory pathway between of nitrogen application and non-nitrogen application,before and after the post-nutrition period conditions.（1）Nitrogen application during the post-fruit vegetative period can significantly increase the bud number in L.chinensis.Nitrogen application,the genes directly or indirectly related to bud formationwere upregulated by 18399 and down by 10732 under the condition of q<0.05and|log_2ratio|≥1,RPKM（Reads per kilobase per million mapped reads）>0.3,while genes closely related to bud formation were up-regulated by 3855 genes and down-regulated by1839 genes when the threshold was q<0.001 and|log_2ratio|≥1,RPKM≥1.Finally,the result shows that the gene regulation the amount of axillary shoot buds was directly related to the related pathways of cytokinin synthesis and metabolism in hormone metabolism,polysaccharide hydrolysis in primary metabolism,and glycolysis energy utilization.（2）The trade-offs of energy distribution at the base of tillering during the fruiting stage and post-fruit vegetative period are the deeper reasons that affect the production of underground buds.Compared with the fruiting period,the primary metabolism and secondary metabolism of the tillering base were increased,that is,the L.chinensis increased the energy input to the tillering base during the post-fruit nutrition period.An increase of the energy input into secondary metabolism can be prevent insect feeding and other disturbances to interfere with bud formation and differentiation.（3）Nitrogen application will promote the primary metabolic process of the tillers base at the post-fruit vegetative and fruiting stages,but reduce the secondary metabolics.That is,when nitrogen is adequate,the base of the tiller will allocate more energy for the production of buds and reduce the secondary metabolism to defense unfavorable environment.Nitrogen application could be changed the trade-off relationship between growth and defense of tiller base.In summary,nitrogen increases axillary shoot bud in the fall is related to nitrogen application increase the energy input of the primary tiller base for the primary metabolism and reduce the energy input to secondary metabolism during the fruiting and post-fruit vegetative periods.This study not only provides important informations to better understand the occurrence mechanism of the belowground bud bank in the view of gene regulation in L.chinensis,but also and provides a scientific theoretical supports for further increase the seed and hay yield by regulating the occurrence of bud bank.