Unraveling the role of TCP and GLK transcription factors in Arabidopsis seedling development

ALEM, ANTONELA L; GONZALEZ, DANIEL H; VIOLA, IVANA L

Congreso; RAFV Conference 2023, XXXIV Argentinian Meeting of Plant Physiology; 2023

Sociedad Argentina de Fisiología Vegetal

Following germination, exposure to light promotes cotyledon opening and expansion and chloroplastdevelopment in a process called de-etiolation. Golden2-like (GLK) proteins are members of the GARP family of MYB transcription factors that play essential roles in chloroplast development. TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) transcription factors participate in several plant development processes, as embryogenesis, germination, flowering, immunity, and hormonal signaling. They can be grouped into two major classes, I and II. In previous studies, we found that Golden2-like 1 (GLK1) physically interacts with several class I TCPs. Furthermore, our findings demonstrate that the class I protein TCP15 and GLK1 are jointly required for cotyledon opening and the induction of cell expansion and photosynthesis-associated genes during de-etiolation of Arabidopsis seedlings. In this study, we explored the connection between GLK1 and class II TCPs during de-etiolation. We found that a class II TCP mutant showed a delay in the opening of cotyledons after light exposition. Moreover, we observed that expression of light-responsive genes involved in cotyledon opening and chloroplast development was significantly affected in this mutant. However, different to class I TCPs, protein-protein interactions were not detected between the class II TCP members and GLK1. Further molecular and genetic analyses of loss-of-function mutants and gain-of-function constitutive overexpression transgenic lines for these genes revealed a regulatory network where these transcription factors interconnect to promote cotyledons opening and the establishment of the photosynthetic apparatus, suggesting that class I and II TCPs integrate the regulatory network affected by GLK transcription factors by acting at different levels. In summary, this study provides new insights into the coordinated functions of TCP and GLK families during Arabidopsis seedling development