Abstract
BackgroundThe tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most economically important woody crops. Recently, many leaf color genotypes have been developed during tea plant breeding and have become valuable materials in the processing of green tea. Although the physiological characteristics of some leaf color mutants of tea plants have been partially revealed, little is known about the molecular mechanisms leading to the chlorina phenotype in tea plants.ResultsThe yellow-leaf tea cultivar Zhonghuang 2 (ZH2) was selected during tea plant breeding. In comparison with Longjing 43 (LJ43), a widely planted green tea cultivar, ZH2 exhibited the chlorina phenotype and displayed significantly decreased chlorophyll contents. Transmission electron microscopy analysis revealed that the ultrastructure of the chloroplasts was disrupted, and the grana were poorly stacked in ZH2. Moreover, the contents of theanine and free amino acids were significantly higher, whereas the contents of carotenoids, catechins and anthocyanin were lower in ZH2 than in LJ43. Microarray analysis showed that the expression of 259 genes related to amino acid metabolism, photosynthesis and pigment metabolism was significantly altered in ZH2 shoots compared with those of LJ43 plants. Pathway analysis of 4,902 differentially expressed genes identified 24 pathways as being significantly regulated, including ‘cysteine and methionine metabolism’, ‘glycine, serine and threonine metabolism’, ‘flavonoid biosynthesis’, ‘porphyrin and chlorophyll metabolism’ and ‘carotenoid biosynthesis’. Furthermore, a number of differentially expressed genes could be mapped to the ‘theanine biosynthesis’, ‘chlorophyll biosynthesis’ and ‘flavonoid biosynthesis’ pathways. Changes in the expression of genes involved in these pathways might be responsible for the different phenotype of ZH2.ConclusionA novel chlorophyll-deficient chlorina tea plant cultivar was identified. Biochemical characteristics were analyzed and gene expression profiling was performed using a custom oligonucleotide-based microarray. This study provides further insights into the molecular mechanisms underlying the phenotype of the chlorina cultivar of Camellia sinensis.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-014-0352-x) contains supplementary material, which is available to authorized users.
Highlights
The tea plant (Camellia sinensis (L.) O
Zhonghuang 2 (ZH2) exhibits yellow new shoots, which differs from what occurs in Longjing 43 (LJ43), a green tea cultivar that is widely planted in China (Figure 1A and B)
20% of the contents in LJ43, respectively; Figure 1C). These results suggested that the yellow leaves of ZH2 result from reduced chlorophyll levels and that the lower chlorophyll content of ZH2 might result from abnormal chlorophyll biosynthesis
Summary
The tea plant (Camellia sinensis (L.) O. Kuntze) is one of the most economically important woody crops. Many leaf color genotypes have been developed during tea plant breeding and have become valuable materials in the processing of green tea. Kuntze), which is cultivated for the production of a non-alcoholic beverage, is one of the most economically important woody crops worldwide [1]. Many leaf color cultivars have recently been developed during tea plant breeding and have become valuable materials in the processing of green tea. Higher total free amino acid concentrations are detected in the leaves of these two cultivars compared with regular green tea leaves [4,8]. The albino tea cultivars have received increased attention and are popular with tea consumers in China because of their unique leaf color and abundant free amino acids
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