Fruit ripening mutants reveal cell metabolism and redox state during ripening.

Ripening which leads to fruit senescence is an inimitable process characterized by vivid changes in color, texture, flavor, and aroma of the fleshy fruits. Our understanding of the mechanisms underlying the regulation of fruit ripening and senescence is far from complete. Molecular and biochemical studies on tomato (Solanum lycopersicum) ripening mutants such as ripening inhibitor (rin), nonripening (nor), and never ripe (Nr) have been useful in our understanding of fruit development and ripening. The MADS-box transcription factor RIN, a global regulator of fruit ripening, is vital for the broad aspects of ripening, in both ethylene-dependent and independent manners. Here, we have carried out microarray analysis to study the expression profiles of tomato genes during ripening of wild type and rin mutant fruits. Analysis of the differentially expressed genes revealed the role of RIN in regulation of several molecular and biochemical events during fruit ripening including fruit specialized metabolism and cellular redox state. The role of reactive oxygen species (ROS) during fruit ripening and senescence was further examined by determining the changes in ROS level during ripening of wild type and mutant fruits and by analyzing expression profiles of the genes involved in maintaining cellular redox state. Taken together, our findings suggest an important role of ROS during fruit ripening and senescence, and therefore, modulation of ROS level during ripening could be useful in achieving desired fruit quality.