A Minimalist Core and Lineage-Specific Expansion Underpin the Adaptive Evolution of the Cyclic Nucleotide-gated Channel (CNGC) Family: Insights from the Tea ( Camellia sinensis ) Pan-Genome

Cyclic nucleotide-gated channels (CNGCs) are critical Ca 2+ -permeable cation channels that orchestrate plant stress responses, yet their evolutionary dynamics in tea plants ( Camellia sinensis ) remain unknown. Here we dissect the CNGC family using a pan-genome of 28 tea accessions. We identified 867 CNGC genes into 30 orthogroups, revealing a dual evolutionary strategy: an ultraconstrained, two-gene core ( CsCNGC8/17 ) under strong purifying selection ensuring signaling fidelity, and Group IVc─a novel clade (39.4% of the family)─exhibiting lineage-specific motif reconfiguration, dispersed duplications and elevated Ka/Ks ratios. Expression profiling suggested that Group IVc members are broadly upregulated across multiple stresses, whereas core genes display condition-specific responses. This unique architecture─balancing a minimalist, conserved core with a massively expanded, plastic periphery─provides a robust adaptive solution to the lifelong stress exposure characteristic of perennial tea plants. These findings offer critical insights into stress-response evolution and valuable molecular targets for breeding resilient tea cultivars.