Effect Of Photoperiod On Flowering Physiology On Camellia Oleifera And Differential Gene Expression Analysis

Camellia oleifera(C.oleifera)is one of the world’s four major woody oilseed species and also an important economic tree species in southern China.The phenomenon of ’many flowers and few fruits,low fruit set rate and yield’ exists in C.oleifera production,one of the main reasons for this phenomenon is that C.oleifera is prone to cloudy rainy weather during the flowering period,which affects the length of sunlight and not conducive to pollination.Photoperiod,as an important flowering regulation pathway,has an important influence on plant growth and flowering.In the case of economic species,flowering is closely related to the subsequent fruiting rate.There are still gaps in research on the photoperiod of C.oleifera,and it’s not clear whether C.oleifera is a short-day,sun-neutral or long-day plant.In order to explore the effect of photoperiod on the flowering physiology of C.oleifera and the key genes of photoperiod response,also to provide a theoretical basis for further research on the mechanism of photoperiod regulation of C.oleifera flowering,this study used ’Huashuo’C.oleifera as the experimental material and set up five photoperiod treatments(8 h/16 h,10 h/14 h,12 h/12 h,14 h/10 h,16 h/8 h),using natural light as the control group(CK).To compare the growth and flowering of C.oleifera under different photoperiodic conditions,the changes in nutrient and endogenous hormone contents,and screen for key signalling pathways and key candidate genes in response to photoperiodic conditions.The main results are as follows:(1)The results showed that,compared to CK,the plant height of C.oleifera under the long daylight treatment was significantly higher,flowering time was earlier and also more flower numbers.the plant height of C.oleifera under the short daylight treatment was significantly lower,flowering time was later and also less flower numbers.(2)The chlorophyll,soluble sugar and soluble protein contents of C.oeifera leaves were measured at flowering stage in each treatment group.The results showed that compared with CK,the chlorophyll,soluble sugar and soluble protein contents of C.oleifera leaves in the long daylight treatment increased significantly,while the chlorophyll,soluble sugar and soluble protein contents of C.oleifera leaves in the short daylight treatment decreased significantly.Combined with the analysis of the plant height,flowering time and number of flowers in each treatment group,it illustrated that long daylight stimulated the accumulation of chlorophyll,soluble sugar and soluble protein during flowering,which was beneficial to the growth and development of the plant,while short daylight inhibited the accumulation of these three nutrients in C.oleifera,which was detrimental to the growth and development of the plant.(3)The IAA,ABA,GA3 and CTK contents of C.oleifera leaves under each treatment at flowering stage were measured.The results showed that compared to CK,the IAA and ABA contents of C.oleifera under the long daylight treatment were significantly increased,while the GA3 and CTK contents of compared to CK under the short daylight treatment were significantly increased.In addition,the values of IAA/GA3 and ABA/CTK were higher in compared to CK under long daylight treatment,while the values of ABA/GA3 and ABA/IAA+GA3+CTK were higher in C.oleifera under short daylight treatment.Combined with the species variability in endogenous hormone regulation of plant growth and development and the flowering characteristics of C.oleifera in each treatment group in this experiment,it’s hypothesized that long daylight exposure promotes flowering development of C.oleifera by inducing high levels of IAA and ABA,and low levels of GA3 and CTK in C.oleifera leaves,and regulating the balance of IAA,ABA,GA3 and CTK hormones.(4)Through transcriptomic analysis,a total of 3475 differentially expressed genes(DEGs)were screened in the photoperiodic comparator groups of C.oleifera in this study.The results showed that the short and long daylight treatment groups had the highest number of DEGs(1680 genes),including 730 up-regulated genes and 950 down-regulated genes.Through the KEGG(Kyoto Encyclopedia of Genes and Genomes)biological pathway enrichment analysis to 3475 DEGs,it showed that the above DEGs were significantly enriched in flavonoid biosynthesis,amino and nucleotide sugar metabolism and circadian-vegetative pathways.In addition,eight hub genes,namely GI,AP2,WRKY65,SCR,SHR,PHR1,ERF106 and SCL3,were identified as potentially involved in the photoperiodic flowering mechanism of C.oleifera.