The Spatiotemporal Variations of L-glutamic Acid and Catechins During the Development of Etiolated Tea Leaves in ‘Huangjinye’

The distinct qualities of etiolated leaves from chlorotic tea cultivars are significantly related to their developmental stages during harvesting. In this study, Hjy (Camellia sinensis L. cv. Huangjinye) as a light sensitive etiolated tea variety had a higher concentration of theanine (99.36 mg/g) and lower total catechins (119.15 mg/g) than normal green tea plant. The shading treatment could turn the yellow leaves to green and alter the levels of catechins, caffeine, and theanine of tea shoots in Hjy. Additionally, the buds and 2nd leaves of Hjy tea shoots had the highest content of theanine, whereas the 3rd leaves contained the highest caffeine and total catechins. Moreover, the three different developmental stages of Hjy tea leaves had different levels of pigments, total free amino acids, total polyphenols, and soluble protein. Transcriptome and metabolome analyses identified a total of 58,175 genes and 414 metabolites in the three developmental stages, which were most enriched in photosynthesis, primary metabolism, lipid metabolism, and flavonoid metabolism. The multi-omics analysis revealed that the accumulations of L-glutamic acid and L-glutamine were up-regulated by GOGATs and GDHs and down-regulated by GSs, TS, and ALaDC. WRKY24, WRKY27, MYB105, and some other genes related to plant development and ion balance were highly correlated with L-glutamic acid biosynthesis. The decreased expressions of LARs and ANRs contributed to the reduction of catechin, epigallocatechin, and epigallocatechin gallate. WRKY35, WRKY53, MYB62, and some other genes related to photosynthesis, plant development, monooxygenases, and glycosylation exhibit roles in regulating catechins biosynthesis. This study provided the novel information about the Hjy tea plant, and the integrated strategy of multi-omics allowed a mechanistic understanding of the differential accumulation of L-glutamic acid and catechins during the development of etiolated tea leaves.