Abstract
Leaf senescence is a highly-programmed developmental process regulated by an array of multiple signaling pathways. Our group previously reported that overexpression of the protein phosphatase-encoding gene SSPP led to delayed leaf senescence and significantly enhanced cytokinin responses. However, it is still unclear how the delayed leaf senescence phenotype is associated with the enhanced cytokinin responses. In this study, we introduced a cytokinin receptor AHK3 knockout into the 35S:SSPP background. The phenotypic analysis of double mutant revealed that AHK3 loss-of-function reversed the delayed leaf senescence induced by SSPP. Moreover, we found the hypersensitivity of 35S:SSPP to exogenous cytokinin treatment disappeared due to the introduction of AHK3 knockout. Collectively, our results demonstrated that AHK3-mediated cytokinin signaling is required for the delayed leaf senescence caused by SSPP overexpression and the detailed mechanism remains to be further elucidated.
Highlights
Senescence represents the final stage of leaf development, featured by degradation and recycling of nutrients in senescent leaves to actively growing organs [1]
We previously found that overexpression of a PP2C type protein phosphatase-encoding gene
These results indicated that knockout of AHK3 reversed the senescence in SSPP overexpressing Arabidopsis
Summary
Senescence represents the final stage of leaf development, featured by degradation and recycling of nutrients in senescent leaves to actively growing organs [1]. SSPP led to significantly delayed leaf senescence and enhanced cytokinin responses in Arabidopsis [13]. It remains largely unknown how SSPP-mediated delayed leaf senescence signaling is associated with cytokinin signaling. The hypersensitivity of 35S:SSPP to exogenous cytokinin treatment is lost in ahk3-3/35S:SSPP These results together indicate that AHK3-mediated cytokinin signaling is required for the delayed leaf senescence induced by SSPP overexpression. 2019, 20, x FOR PEER REVIEW results together indicate that AHK3-mediated cytokinin signaling is required for the delayed 2leaf. Sci. 2019, 20, 2043 of 7 senescence induced by SSPP overexpression
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