Cloning and Expression Analysis of a MADS-box Gene CsAGL8 in the Tea Plant (Camellia sinensis)

Purpose To clone the CsAGL8 gene sequence of tea plant and to explore the relationship between this gene and tea plant dormancy.

Methods The MADS-box transcription factor family gene CsAGL8 was cloned from the dormant buds of the tea cultivar ‘Emei Wenchun’ by RT-PCR, and bioinformatics analysis such as BLAST comparison was performed. The relative expression levels in eight tissue samples and during overwintering were determined by qPCR. Genetic transformation of Arabidopsis thaliana, to observe the phenotype of transgenic plants and analyze the flowering-related genes.

Results The CDS of CsAGL8 was 720 bp, which encoded 239 amino acids, and contained a highly conserved MADS-box domain and a semi-conserved K-box domain. CsAGL8 showed the highest similarity to AtAGL8 from A. thaliana. The coding region of CsAGL8 showed polymorphisms, and many cis-acting elements such as light, hormone, and stress response were found in the promoter region. Expression analysis showed that CsAGL8 was expressed in different tissues of tea plants, and the highest expression was detected in the dormant terminal buds. During the overwintering process, the expression of CsAGL8 increased first and then decreased. Compared with the regular tea cultivar, the expression levels of CsAGL8 were not only significantly lower, but also down-regulated earlier in the buds of the extra-early cultivar ‘Emei Wenchun’. Overexpression of CsAGL8 in A. thaliana promoted early flowering for 10-15 days.

Conclusion CsAGL8 may be involved in the regulation of winter dormancy in tea plants.