Features of the Functioning of Succinate Dehydrogenase and Malate Dehydrogenase in Leaves of Spinach (Chenopodium foliosum L.) and Amaranth (Amaranthus caudatus L.) under Salt Stress Conditions

Abstract

Salt stress was shown to cause changes in the activity and isozyme composition of mitochondrial malate dehydrogenase (MDH) in leaves of amaranth (C4-type); these changes were manifested in the induction of an additional MDH isoform. Exposure of spinach plants (C3-type) to a NaCl solution did not cause significant changes in the isozyme composition and activity of the enzymes studied. Succinate dehydrogenase (SDH) activity in amaranth leaves under salt stress conditions increased several times, while the isoenzyme composition of SDH remained unchanged. The levels of gene transcripts in leaves of amaranth and spinach clearly correlated with changes in the MDH and SDH activity. Salt stress enhanced expression of the mdh-mtx (mitochondrial) and mdh-cyt (cytoplasmic) genes in amaranth leaves during the whole experiment. In the case of the sdha gene, a decrease in the content of transcripts was observed that clearly correlated with the reduction in SDH activity.