CsEXL3 regulate mechanical harvest-related droopy leaves under the transcriptional activation of CsBES1.2 in tea plant

Abstract

Due to a labor shortage, the mechanical harvesting of tea plantations has become a focal point. However, mechanical harvest efficiency was hampered by droopy leaves, leading to a high rate of broken tea shoots and leaves. Here, we dissected the genetic structure of leaf droopiness in tea plants using genome-wide association studies (GWAS) on 146 accessions, combined with transcriptome from two accessions with contrasting droopy leaf phenotypes. A set of 16 quantitative trait loci (QTLs) containing 54 SNPs and 34 corresponding candidate genes associated with droopiness were then identified. Among these, CsEXL3 (EXORDIUM-LIKE 3) from Chromosome 1 emerged as a candidate gene. Further investigations revealed that silencing CsEXL3 in tea plants resulted in weaker vascular cell malformation and brassinosteroid-induced leaf droopiness. Additionally, brassinosteroid signal factor CsBES1.2 was proved to participate in CsEXL3-induced droopiness and vascular cell malformation via using the CsBES1.2-silencing tea plant. Notably, CsBES1.2 bound on the E-box of CsEXL3 promoter to transcriptionally activate CsEXL3 expression as CUT&TAG based ChIP-qPCR and ChIP-seq suggested in vivo as well as EMSA and Y1H indicated in vitro. Furthermore, CsEXL3 instead of CsBES1.2 decreased lignin content and the expressing levels of lignin biosynthesis genes. Overall, our findings suggest that CsEXL3 regulates droopy leaves, partially through the transcriptional activation of CsBES1.2, with the potential to improve mechanical harvest efficiency in tea plantations.

Acknowledgements

This work was supported by grants from the National Key Research and Development Program of China (2022YFD1200505-2), Zhejiang Provincial Natural Science Foundation of China (LQ23C160010), and China Agriculture Research System of MOF and MARA (CARS-19).

Author contributions

H.L. and L.D. conceived, designed, and performed all the experiments. J.J., R.H., X.X., Y.L., and S.C. performed molecular experiments. J.M. and J.C. performed GWAS and analysed data. M.Y. and L.C. designed experiments and provided the direction of the research. H.L. wrote the manuscript. All authors approved the manuscript.

Data availability

The accession numbers for the key genes described in this report are as follows: CsEXL3 (CSS0040385), CsBES1.2 (CSS0038858). The data for RNA-seq and ChIP-seq can be found in NCBI with the accession number PRJNA1075292. The genome data of 146 tea accessions for GWAS (Table S7, see online supplementary material) can be downloaded in TeaGVD (http://www.teaplant.top/teagvd) [30].

Conflict of interest statement

The authors declare that they have no conflict of interest.

Supplementary data

Supplementary data is available at Horticulture Research online.

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