| Popis: |
Chloroplasts are the site of photosynthesis. In land plants, chloroplast biogenesis is regulated by a family of transcription factors namedGOLDEN2-like(GLK). In C4grasses, it has been hypothesized that genome duplication events led to the sub-functionalization ofGLKparalogs (GLK1andGLK2) to control chloroplast biogenesis in two distinct cell types: mesophyll and bundle sheath cells. Although previous characterization ofgolden2(g2) mutants in maize has demonstrated a role forGLK2paralogs in regulating chloroplast biogenesis in bundle sheath cells, the function ofGLK1has remained elusive. Here we show that, contrary to expectations,GLK1is not required for chloroplast biogenesis in mesophyll cells of maize. Comparisons between maize andSetaria viridis, which represent two independent C4origins within the Poales, further show that the role ofGLKparalogs in controlling chloroplast biogenesis in mesophyll and bundle sheath cells differs between species. Despite these differences, complementation analysis revealed thatGLK1andGLK2genes from maize are both sufficient to restore functional chloroplast development in mesophyll and bundle sheath cells ofSetaria viridismutants. Collectively our results suggest an evolutionary trajectory in C4grasses whereby both orthologs retained the ability to trigger chloroplast biogenesis butGLK2adopted a more prominent developmental role, particularly in relation to chloroplast activation in bundle sheath cells. |
