A Regulatory Circuit between AGL103 and TCPs Balances Growth and Stress Tolerance in Arabidopsis thaliana.

Abstract

Plants must balance growth with stress adaptation, yet the transcriptional mechanisms governing this trade-off remain incompletely defined. Here, we identify the MADS-box transcription factor (TF) AGL103 as a promoter of growth but a negative regulator of drought and salt tolerance in Arabidopsis thaliana. agl103 mutants exhibit enhanced germination, root elongation, and survival under mannitol-induced osmotic stress and salt stress, whereas AGL103-overexpressing plants are hypersensitive. Transcriptomic and molecular analyses show that AGL103 directly represses MYB15 and MYB102 by binding CArG motifs in their promoters. Notably, AGL103 also physically interacts with Teosinte branched 1/Cycloidea/ Proliferating cell factor (TCP) proteins TCP14 and TCP15, forming a repressor complex that reinforces MYB15/MYB102 suppression and antagonizes TCP14-mediated transcriptional activation. Furthermore, TCP14, but not TCP15, feeds back to repress AGL103 transcription, establishing a regulatory loop that fine-tunes plant growth and stress responses. This AGL103-TCPs module integrates developmental and stress signaling, offering mechanistic insight into how plants balance growth and resilience and highlighting potential targets for engineering stress-tolerant crops.