Comparative transcriptome analysis of Agrobacterium tumefaciens reveals the molecular basis for the recalcitrant genetic transformation of Camellia sinensis L

Authors: JIN, KE - Hunan Agricultural University; TIAN, NA - Hunan Agricultural University; Ferreira, Jorge; Sandhu, Devinder; XIAO, LIZHENG - Hunan Agricultural University; GU, MEIYI - Hunan Agricultural University; LUO, YIPING - Hunan Agricultural University; ZHANG, XIANGQIN - Hunan Agricultural University; LIU, GUIZHI - Hunan Agricultural University; LIU, ZHONGHUA - Hunan Agricultural University; HUANG, JIANAN - Hunan Agricultural University; LIU, SHUOQIAN - Hunan Agricultural University

Submitted to: Biomolecules EISSN 2218-273X
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2022
Publication Date: 5/11/2022
Citation: Jin, K., Tian, N., Ferreira, J.F.S., Sandhu, D., Xiao, L., Gu, M., Luo, Y., Zhang, X., Liu, G., Liu, Z., Huang, J., Liu, S. 2022. Comparative transcriptome analysis of Agrobacterium tumefaciens reveals the molecular basis for the recalcitrant genetic transformation of Camellia sinensis L. Biomolecules. 12(5). Article 688. https://doi.org/10.3390/biom12050688.
DOI: https://doi.org/10.3390/biom12050688

Interpretive Summary: Tea is a widely cultivated and commercially valuable crop. Tea leaves are processed into beverages or food additives rich in flavonoids with known health benefits. The tea plant has a long growth cycle and low success rate for hand pollination, two major factors that restrict the improvement of cultivars through conventional cross-breeding. Therefore, novel breeding technologies, such as molecular breeding, are urgently needed to enhance breeding efficiency in tea. Agrobacterium-mediated transformation (AMT) is a fundamental approach to plant genetic engineering, to gene-function elucidation, validation, and the generation of transgenic plants with desired traits. However, AMT has a very low efficiency in tea plants. Functional analysis of the genes responsible for this low efficiency is still lacking. By comparing tea with tobacco, we found several possible pathways, by which the efficiency of genetic transformation of tea plants was decreased. The information generated in this study will be beneficial to geneticists and molecular biologists seeking to improve the efficiency of AMT in tea for purposes of improving breeding of this globally important, economically valuable crop.

Technical Abstract: Tea (Camellia sinensis L.), an important economic crop, is recalcitrant to Agrobacterium-mediated transformation (AMT), which has seriously hindered the progress of molecular research on this species. The mechanisms leading to low efficiency of AMT in tea plants, related to the morphology, growth, and gene expression of Agrobacterium tumefaciens during tea-leaf explant infection, were compared to AMT of Nicotiana benthamiana leaves in the present work. Scanning electron microscopy (SEM) images showed that tea leaves induced significant morphological aberrations on bacterial cells and affected pathogen–plant attachment, the initial step of a successful AMT. RNA sequencing and transcriptomic analysis on Agrobacterium at 0, 3 and 4 days after leaf post-inoculation resulted in 762, 1923 and 1656 differentially expressed genes (DEGs) between the tea group and the tobacco group, respectively. The expressions of genes involved in bacterial fundamental metabolic processes, ATP-binding cassette (ABC) transporters, two-component systems (TCSs), secretion systems, and quorum sensing (QS) systems were severely affected in response to the tea-leaf phylloplane. Collectively, these results suggest that compounds in tea leaves, especially gamma-aminobutyrate (GABA) and catechins, interfered with plant–pathogen attachment, essential minerals (iron and potassium) acquisition, and quorum quenching (QQ) induction, which may have been major contributing factors to hinder AMT efficiency of the tea plant.