Impairment of the photorespiratory pathway on tomato leaves during the infection process of Septoria lycopersici

Abstract

Septoria leaf spot, caused by Septoria lycopersici, is a destructive disease on tomato that reduces fruit quality and yield. Plants infected by pathogens display profound changes in photosynthesis, photorespiration, and respiration that affect defense responses. This study investigated the impacts caused by S. lycopersici infection on the photorespiration of tomato plants. Infected leaves showed a remarkable reduction in photosynthesis and in the pool of photosynthetic pigments. The respiration and photorespiration-to-gross photosynthesis ratio increased in the infected leaves. Reduction in photosynthesis on infected leaves was mainly associated with biochemical limitations. Infection by S. lycopersici resulted in increased concentrations of malonaldehyde, superoxide anion, and hydrogen peroxide indicating great oxidative damage. Genes involved in the photorespiratory pathway (GOX1, GOX2, SHMT2, SMHT3, and GLYK), nitrogen metabolism (Fd-GOGAT), and stress acclimatization (mMDH1, mMDH2, and CAT) were up-regulated during the infection process of S. lycopersici. A better comprehension of the physiological changes in tomato leaves infected by S. lycopersici at the photorespiration level may contribute to breeding cultivars with increased resistance to cope with Septoria leaf spot.