The plastid hexokinase pHXK: A node of convergence for sugar and plastid signals in Arabidopsis

The inhibitors to plastid gene expression (PGE) were effective in preventing nuclear photosynthetic gene expression only if applied within the first 2–3 days of Arabidopsis seedling development. However, the signal transduction processes are still unknown. In this investigation, we found 3% glucose with 1 mM chloramphenicol co-treatment repressed LHCB transcript significantly in mature Arabidopsis seedlings, while effective solo glucose treatment needed a concentration of 7%. The repressive effects of glucose and chloramphenicol on LHCB expression were inhibited in phxk (plastid hexokinase) mutant. pHXK enzyme activities, location, function in signal transduction, and cross talk to plastid GUN1 protein (a key signaling factor) were also investigated. The data suggest that pHXK may be a node of convergence for sugar-mediated and PGE-derived signals in Arabidopsis.