The antagonistic effect of AtCCR4a upon drought or heat stress conditions

Abstract

Climate changes are expected to increase the severity of environmental adversities to plants, such as changes in rainfall regimes and the occurrence of more extreme temperatures, imposing a major risk to the productivity of agricultural crops. Throughout evolution, plants have evolved elegant mechanisms to cope with different adverse conditions, through the activation of different signaling pathways. The occurrence of abiotic stresses, such as osmotic stress or endoplasmic reticulum stress, tend to activate specific cellular pathways, such as the death cell signaling pathway mediated by proteins that contain DCD/NRP domains. The AtNRP1 and AtNRP2 proteins, components of the pathway in Arabidopsis, have been characterized as effectors of the programmed cell death process by the breakdown of the vacuolar membrane. Understanding how this pathway is integrated into cellular stability is essential, which justifies checking the predicted and not yet functionally characterized interactions among the components of the pathway with other proteins, such as AtCCR4a, a deadenylase that is both active in mRNA processing and in sucrose/starch metabolism. Given this context, we aimed to investigate the interaction between AtNRP2 and AtCCR4a, and its role during heat and drought stresses. We did not observe its direct involvement in the NRP-signaling pathway, however AtCCR4a was induced by osmotic and heat stresses. Furthermore, AtCCR4a disruption provides a drastically heat stress-sensitive phenotype, leading to reductions in photosynthetic pigment contents days after exposure to stress and negative changes in carbohydrate metabolism during this condition. Surprisingly, AtCCR4a disruption also promotes a more tolerant phenotype to water deficit, contributing to greater maintenance of relative water contents in leaf tissues and plant survival rate. These results indicate that AtCCR4a may have an antagonistic function in stress-responsive pathways, probably by regulating at a post-transcriptional level the expression of certain genes and/or by selecting specific target mRNAs. Keywords: Abiotic. Arabidopsis. Deadenylase. Heat. Water.