CRF2 and its role in cytokinin response and abiotic stress

Abstract

Cytokinin Response Factors are a small family of plant transcription factors originally discovered in a screen for genes whose expression is controlled by cytokinin. Cytokinin is a plant hormone known to be involved in developmental processes such as root-shoot patterning, and delaying senescence. It functions through a modified two-component signalling cascade, which is reviewed in Chapter II. Cytokinin has also been implicated in stress response, which has been examined in both Arabidopsis and tomato with specific CRFs. Cytokinin has been shown to attenuate signs of physiological stress, such as decrease in photosynthesis and production of reactive species. In studying this, cytokinins have either been externally applied or genes creating cytokinin are overexpressed in planta. A key element of this research has been to examine the plant’s native levels of cytokinin with response to stress. We see levels increasing when WT seedlings are exposed to salt (150 mmol NaCl). When crf2 is exposed to the same treatment, we see a direct contrast; there is a decrease in CK levels. RNA-seq was run at the same time and showed differential expression of 8,014 genes between WT and crf2 when comparing transcripts expressed in control vs salt treatment. In tomato, cytokinin measurements and RNA-seq were done to analyze differences in cytokinin levels and gene-expression between two types of abiotic stress: salt and oxidative. Salt showed an increase in CK levels while hydrogen peroxide showed a decrease. Additionally, transcriptomes showed 6,643 DE transcripts between treated tissues. These data indicate that although abiotic stress is frequently thought to underlie similar reactions physiologically, this may not be the case.