Expression of LHC Genes and their Relation to Photo-Oxidative Stress Tolerance Tolerance in Solanum lycopersicum L. and Solanum chilense (Dunal) Reiche
Simultaneous exposition to low temperature and high light radiation cause photoinhibition of photosynthetic apparatus, affecting the productivity and geographical distribution of agricultural crops. In several Solanaceous species, tolerance to low temperature stress in combination with high light has been associated with some stimulation in non-photochemical quenching (NPQ), which involved reorganization in light-harvesting complex (LHC) proteins. To study photosynthetic performance in Solanum lycopersicum L. and S. chilense (Dunal) Reiche, and to investigate transcriptional regulation of genes encoding LHC proteins and their involvement in the NPQ, plants of both species were exposed to low temperature (4 °C) and high light radiation (1300 /<mol m-2 s-1). Lipid peroxidation, photochemical efficiency, and changes in xanthophyll cycle pigments were measured. The results presented here indicate that S. chilense showed higher tolerance to photoinhibition than S. lycopersicum under low-temperature and high light conditions, increasing light-energy consumption in photochemical processes by increasing photosynthetic capacity as indicated by photochemical quenching (qP) and relative electron transport rate (ETR) parameters. The contribution of light-harvesting chlorophyll a/b binding (LHC) protein was not related to dissipate excess excitation energy as heat (NPQ), but rather with the antioxidant function attributable to zeaxanthin as indicated by the amount of peroxidized lipids in S. chilense. We suggest that the differential expression of Lhcal transcripts, with zeaxanthin binding sites could contribute to the greater tolerance of S. chilense to photoxidative stress.