Regulatory networks established by TCP and GLK transcription factors during Arabidopsis seedling development

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

Congreso; LVIII Reunión Anual de SAIB; 2022

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

After germination, light exposure promotes cotyledon opening and expansion and chloroplast development in a process called de-etiolation. Golden2-like (GLK) proteins are members of the GARP family of MYB transcription factors involved in chloroplast development, immunity and senescence. TEOSINTE-BRANCHED1/CYCLOIDEA/PCF (TCP) proteins constitute a family of transcription factors that control various processes of plant development such as embryogenesis, germination, and morphogenesis of leaves and flowers. They also function in plant immunity and hormonal signaling. They can be grouped into two major classes, I and II. In Arabidopsis, the TCP family consists of 24 members, 13 belonging to class I and 11 to class II, whereas GLK genes exist as pairs, GLK1 and GLK2. In previous studies, we found that GLK1 interacts with several class I TCPs. Moreover, we reported 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 analyzed the relationship between GLK transcription factors and class II TCPs during de-etiolation. We found that mutants in a class II TCP from Arabidopsis showes a delay in the opening of cotyledons when exposed to light and decreased expression of genes involved in cotyledon opening and chloroplast development, similarly to observations made in GLK1 and TCP15 mutant plants. However, protein-protein interaction between GLK1 and class II TCP members was not detected in yeast-two-hybrid assays. Further molecular and genetic analyses of loss-of-function mutants and gain-of-function constitutive overexpression transgenic lines for these genes revealed that they act by regulating the expression of similar groups of light-regulated genes. Moreover, we identified a regulatory network where these transcription factors interconnect to promote the opening of the cotyledons and the establishment of the photosynthetic apparatus. Taken together, this study provides new evidence of the concerted function of the TCP and GLK families during Arabidopsis seedling development and suggest that class I and class II TCPs have incorporated into the regulatory network affected by GLK transcription factors acting at different levels.