SnoRNP is essential for thermospermine-mediated development in Arabidopsis thaliana

摘要

Polyamines have been discovered for hundreds of years and once considered as a class of phytohormones.Polyamines play critical roles in a range of developmental processes.However,the molecular mechanisms of polyamine signaling pathways remain poorly understood.Here,we measured the contents of main types of polyamines,and found that endogenous level of thermospermine(T-Spm)in Arabidopsis thaliana is comparable to those of classic phytohormones and is significantly lower than those of putrescine(Put),spermidine(Spd),and spermine(Spm).We further found a nodule-like structure around the junction area connecting the shoot and root of the T-Spm biosynthetic mutant acl5 and obtained more than 50 suppressors of acl5 nodule structure(san)through suppressor screening.An in-depth study of two san suppressors revealed that NAP57 and NOP56,core components of box H/ACA and C/D snoRNPs,were essential for T-Spm-mediated nodule-like structure formation and plant height.Furthermore,analyses of rRNA modifications showed that the overall levels of pseudouridylation and 2′-O-methylation were compromised in san1 and san2 respectively.Taken together,these results establish a strong genetic relationship between rRNA modification and T-Spm-mediated growth and development,which was previously undiscovered in all organisms.