As a preferred nitrogen form, ammonium (NH4+) transport via specific transporters is particularly important for the growth and development of tea plants (Camellia sinensis L.). However, our understanding of the functions of the AMT family in tea plants is limited. We identified and named 16 putative AMT genes according to phylogenetic analysis. All CsAMT genes were divided into three groups, distributed on 12 chromosomes with only one segmental duplication repetition. The CsAMT genes showed different expression levels in different organs, and most of them were expressed mainly in the apical buds and roots. Complementation analysis of yeast mutants showed that CsAMTs restored the uptake of NH4+. This study provides insights into the genome‐wide distribution and spatial expression of AMT genes in tea plants.

The tea plant is a kind of ammonium-preferring crop, but the mechanism whereby ammonium (NH4+) regulate its growth is not well understood. The current study focused on the effects of NH4+ on tea plants. Transcriptomic analysis was performed to investigate the early- and late-stage NH4+ deprivation and resupply in tea plants shoots. Through short- and long-term NH4+ deficiency, the dynamic response to NH4+ stress was investigated. The most significant effects of NH4+ deficiency were found to be on photosynthesis and gene ontology (GO) enrichment varied with the length of NH4+ deprivation. Enriched KEGG pathways were also different when NH4+ was resupplied at different concentrations which may indicate reasons for tolerance of high NH4+ concentration. Using weighted gene co-expression network analysis (WGCNA), modules related to significant tea components, tea polyphenols and free amino acids, were identified. Hence, NH4+ could be regarded as a signaling molecule with the response of catechins shown to be higher than that of amino acids. The current work represents a comprehensive transcriptomic analysis of plant responses to NH4+ and reveals many potential genes regulated by NH4+ in tea plants. Such findings may lead to improvements in nitrogen efficiency of tea plants.

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