Ke Chen, Kangli Sun, Chanjuan Ye, Yutong Liu, Yanduan Hu, Bin Jia, Shu Jiang, Yi Zou, Rui Cao, Jie Guo, Dagang Chen, Xinqiao Zhou, Juan Liu, Qian Qian, Xin Peng, Mengyuan Shen, Degui Zhou, Si Cheng, Jianing Mi, Qinlong Zhu*, Qi Liu*, Chuanguang Liu*and Jiantao Tan*

Plant Communications

Abstract

Theanine, a bioactive amino acid exclusive to Theaceae plants (e.g., tea), is intrinsically absent in Poaceae cereals due to the lack of key synthetic enzymes. To bridge this metabolic gap, we employed a cross-species synthetic biology strategy: codon-optimized CsAlaDC and CsTS genes from tea (Camellia sinensis) were co-expressed with the rice endogenous OsAlaAT gene to enhance precursor alanine supply. This approach successfully generated theaRice, a novel functional rice accumulating theanine at 100 µg·g⁻¹ dry grain weight，which also significantly elevated GABA levels. Functional validation via animal trials demonstrated that dietary theaRice supplementation markedly enhanced immune parameters in quails, including upregulation of IFN-α and IgM. Concurrently, 16S rRNA sequencing revealed a beneficial shift in gut microbiota composition—characterized by proliferation of probiotic bacteria and suppression of pathogenic taxa. This study represents the first demonstration that oral administration of theaRice can concurrently modulate systemic immunity and intestinal microbiota, establishing a pioneering paradigm for metabolite-engineered crop biofortification and the development of next-generation functional staple foods.