Multi-omics Study On Tea Germplasm Resources And Drought Resistance

Tea plants are suitable for moist environment.With the local climate changed,tea plants are always subjected to various abiotic stresses,such as drought.Drought stress would decrease the yield and quality of tea.It is particularly important to observe the drought-resistant mechanism of tea plants and to breed new drought-resistant varieties.In the present study,we firstly identified two germplasm resources by using metabolomics methods,then systematically explored the molecular regulation mechanism,mainly refers to physiological responses,gene expressions and metabolites profile changes,of exogenous ABA on tea plants under drought stress by using high throughput sequencing technology,broad target metabolome techniques and molecular biology technology.The main results are summarized as follows: 1.We identified two kinds of tea germplasmsby combining the assessment of morphology,biochemistry,metabolomics and sensory evaluation.We found ‘QN3’and ‘QN38’had thefeatures of earlier germination and higher yield as compared with the control cultivar ‘HM’;The contents of tea polyphenols and catechins in QN3 were the highest,the content ofcaffeine in QN38 was lowest;QN3 had a higher catechins metabolic actvity,especially forthe biosynthesis of ECG and EGCG.While the QN38 possesses a higher amino acidsmetabolic actvity;Based on sensory quality evaluation,the total quality scores of green teasprocessed from QN3 and QN38 were both more than 90 points.In summary,we consideredthat QN3 and QN38 colud be two excellent breeding materials with high-yield andhigh-quality for processing green tea.We also concluded that metabolomics approach can bean effective auxiliary method used to evaluate the tea germplasm resources.2.The effects of exogenous ABA on physiological characteristics of tea plants under droughtstress were analyzed.The results showed that exogenous ABA alleviated the accumulationof MDA,mitigated the decrease of maximal PSII efficiency(Fv/Fm),prohibited thedegradation of chlorophyll and increased the activity of glutathione reductase in tea plantunder drought stress condition.3.Differential expression genes(DEGs)related to chlorophyll metabolism,starch and sucrosemetabolism,glycolysis,TCA cycle,glutathione metabolism and flavonoid metabolism wereidentified between ABA vs SD.As a result,we found the expression trends of DEGs wereconsistented with the changes of physiological characteristics as above shown,whichrevealed that exogenous ABA could alleviate the drought stress damage effects on tea plantsthrough activating the antioxidant system,photosynthetic system and energy metabolism oftea plants.4.The metabolite profiles analysis of CK,MD,ABA and SD based on broad target metabolometechniques.A total of 641 metabolites were identified in this study.Differential metabolitesanalysis showed that most of the flavonoids abundances were markedly increased,whilemost of the lipid metabolites were significantly decreased in AT/MD than in SD/MD,indicating that tea plants could adapt to the adverse environment by changing the lipidcomponents when their encounter drought stress,and exogenous ABA may play an importantrole in maintaining the balance of primary metabolism in tea plant under drought stress.Inaddition,exogenous ABA not only regulated the expression of genes related to the flavonoid biosynthesis,but also promoted a large amount of carbon sources fluxed into flavonoid metabolism to produce many different types of flavonoids and derivatives,so that improved the drought tolerance of tea plants.