Yoshiyama, K. O. | bioRxiv Science

bioRxiv2023

Transfer of cyclobutane pyrimidine dimer photolyase to chloroplasts for Poaceae survival under ultraviolet-B radiation

Cyclobutane pyrimidine dimer (CPD) photolyase (PHR), the primary enzyme for repairing the CPD induced by ultraviolet B (UV-B) radiation, is essential for plants living under sunlight. Rice CPD photolyase (OsPHR), is such a unique triple-targeting protein. The signal sequences required for its translocation to the nucleus or mitochondria are located in the C-terminal region but were yet to be identified for chloroplasts. Here, we identified sequences located in the N-terminal region, including the serine-phosphorylation site at position 7 of OsPHR, and found that OsPHR is transported/localized to chloroplasts via a vesicle transport system under the control of serine phosphorylation. However, the sequence identified in this study is only conserved in some Poaceae species and in many other plants, PHR does not localize to chloroplasts Therefore, we reasoned that Poaceae species need the ability to repair CPD in the chloroplast genome to survive under sunlight and have acquired this new mechanism for chloroplast translocation.

cell biology↗

bioRxiv2020

Arabidopsis Casein Kinase 2 triggers Stem Cell Exhaustion under Al Toxicity and Phosphate Deficiency Through activation of the DNA Damage Response pathway

Aluminum (Al) toxicity and inorganic phosphate (Pi) limitation are widespread chronic abiotic and mutually enhancing stresses that profoundly affect crop yield. Both stresses cause a strong inhibition of root growth, resulting from a progressive exhaustion of the stem cell niche. Here, we report on a casein kinase 2 (CK2) inhibitor identified by its capability to maintain a functional root stem cell niche under Al toxic conditions. CK2 operates through phosphorylation of the cell cycle checkpoint activator SUPPRESSOR OF GAMMA RADIATION1 (SOG1), priming its activity under DNA-damaging conditions. In addition to yielding Al tolerance, CK2 and SOG1 inactivation prevents meristem exhaustion under Pi starvation, revealing the existence of a low Pi-induced cell cycle checkpoint that depends on the DNA damage activator ATAXIA-TELANGIECTASIA MUTATED. Overall, our data reveal an important physiological role for the plant DNA damage response pathway under agriculturally limiting growth conditions, opening new avenues to cope with Pi limitation. ONE-SENTENCE SUMMARYCasein kinase 2 and DNA damage response regulators play a pivotal role in the control of Arabidopsis root growth in response to Al toxicity and phosphate limitation.

plant biology↗