The involvement of SIAMESE-RELATED proteins and SUPPRESSOR OF GAMMA RESPONSE 1 in cadmium-induced stress responses in Arabidopsis thaliana leaves

Abstract

Introduction: Cadmium present in polluted soils can be taken up by plants, induce and oxidative challenge and hereby impair their growth. Consequently, Cd influences cell division and endoreduplication, two important processes in plant growth, coordinated by CDK activity, which is regulated by CDK inhibitors such as SMR proteins. Expression of these SMRs, in turn, is regulated by ROS-induced DNA damage via SOG1. This study aimed to unravel whether SOG1, SMR4, SMR5 and SMR7 mediate Cd-induced effects on oxidative stress, DNA damage and cell cycle progression. Methods: the amount of cell division and endoreduplication, expression of oxidative stress and DNA damage related genes and GSH determinations were compared between leaves of WT, smr4/5/7 and sog1-7 A. thaliana plants exposed to 0 or 5 µM Cd in hydroponics using a short-term, long-term and chronic set-up. Results and conclusion: SOG1 is involved in the early Cd-induced inhibition of leaf growth, cell division and endoreduplication, the oxidative stress and DNA damage response and GSH biosynthesis upon Cd exposure. Furthermore, lack of functional SOG1 impairs reproductive growth during chronic Cd exposrue. The role of the SMR proteins is less clear as the Cd effects on the smr4/5/7 mutant displayed little to no differences compared to WT plants. This suggests that the SMR proteins are not involved in regulating Cd-induced effects on leaf growth and the cell cycle. It is possible that a bypass mechniasm is activated in this mutant, which needs further investigation.