Arabidopsis SMO2 modulates ribosome biogenesis by maintaining the RID2 abundance during organ growth

Abstract

Ribosome biogenesis is a process of making ribosomes that is tightly linked with plant growth and development. Here, through a suppressor screen for the smo2 mutant, we found that lack of a ribosomal stress response mediator, ANAC082 partially restored growth defects of the smo2 mutant, indicating SMO2 is required for the repression of nucleolar stress. Consistently, the smo2 knock-out mutant exhibited typical phenotypes characteristic of ribosome biogenesis mutants, such as pointed leaves, aberrant leaf venation, disrupted nucleolar structure, abnormal distribution of rRNA precursors, and enhanced tolerance to aminoglycoside antibiotics that target ribosomes. SMO2 interacted with ROOT INITIATION DEFECTIVE 2 (RID2), a methyltransferase-like protein required for pre-rRNA processing. SMO2 enhanced RID2 solubility in Escherichia coli and the loss of function of SMO2 in plant cells reduced RID2 abundance, which may result in abnormal accumulation of FIBRILLARIN 1 (FIB1) and NOP56, two key nucleolar proteins, in high-molecular-weight protein complex. Taken together, our results characterized a novel plant ribosome biogenesis factor, SMO2 that maintains the abundance of RID2, thereby sustaining ribosome biogenesis during plant organ growth.

Proteomic profiling of Arabidopsis nuclei reveals distinct protein accumulation kinetics upon heat stress

“…Interestingly, STRS1 and 2 are RNA helicases that attenuate the abiotic stress response 54 . LLG also contained nucleolar proteins, PONTIN/RIN1, a plant orthologue involved in telomerase assembly in the nucleolus 55 , and RNA Pol I, II, III and IV common subunit NRPB5 59 , GAR2 and ATRH7 (Arabidopsis RNA HELICASE 75) 60 . Uncharacterized nucleolar proteins, such as Gar1/Naf1 (At3g03920), a subunit of the H/ACA RNP subunit, and U3-containing 90S preribosomal complex subunit (At2g43110), were also found in CG (Table S6 sheet CG C5).…”