The chaperonin 60 protein SlCpn60α1 modulates photosynthesis and photorespiration in tomato.

As an indispensable biological process of plants, photosynthesis produces organic substances for plant growth, during which photorespiration occurs to oxidize carbohydrates to a homeostasis. Although the molecular mechanism underlying photosynthesis and photorespiration has been widely explored, the crosstalk between photosynthesis and photorespiration remains largely unknown. In this study, we isolated and characterized T-DNA insertion mutant of tomato (Solanum lycopersicum) named yellow leaf (yl) with yellowish leaves, retarded growth, and chloroplast collapse that hampered both photosynthesis and photorespiration. Genetic and expression analyses demonstrated that the phenotype of yl was caused by a loss of function mutation resulting from a single copy T-DNA insertion in chaperonin 60α1 (SlCPN60α1). SlCPN60α1 showed high expression levels in leaves and located in both chloroplast and mitochondria. Silencing of SlCPN60α1using the virus-induced gene silencing and RNA interference mimic the phenotype of yl. Two-dimensional electrophoresis (2-DE) and yeast-two hybrid (Y2H) results suggest that SlCPN60α1 potentially interact with proteins which are involved in chlorophyll synthesis, photosynthetic electron transport and the Calvin cycle, and further affect photosynthesis. Moreover, SlCPN60α1 directly interacted with serine hydroxymethyltransferase (SlSHMT1) in mitochondria, thereby regulating photorespiration in tomato. This study outlines the importance of SlCPN60α1 for both photosynthesis and photorespiration and provides molecular insights towards plant genetic improvement.