OsCYP2, a chaperone involved in degradation of auxin‐responsive proteins, plays crucial roles in rice lateral root initiation

Abstract

SUMMARYAuxin plays a pivotal role in many facets of plant development. It acts by inducing the interaction between auxin-responsive [auxin (AUX)/indole-3-acetic acid (IAA)] proteins and the ubiquitin protein ligase SCF TIR to promote the degradation of the AUX/IAA proteins. Other cofactors and chaperones that participate in auxin signaling remain to be identified. Here, we characterized rice (Oryza sativa) plants with mutations in a cyclophilin gene (OsCYP2). cyp2 mutants showed defects in auxin responses and exhibited a variety of auxin-related growth defects in the root. In cyp2 mutants, lateral root initiation was blocked after nuclear migration but before the first anticlinal division of the pericycle cell. Yeast two-hybrid and in vitro pull-down results revealed an association between OsCYP2 and the co-chaperone Suppressor of G2 allele of skp1 (OsSGT1). Luciferase complementation imaging assays further supported this interaction. Similar to previous findings in an Arabidopsis thaliana SGT1 mutant (atsgt1b), degradation of AUX/IAA proteins was retarded in cyp2 mutants treated with exogenous 1-naphthylacetic acid. Our results suggest that OsCYP2 participates in auxin signal transduction by interacting with OsSGT1.

Master and servant: Regulation of auxin transporters by FKBPs and cyclophilins

“…2), and can move from shoot to root in grafted plants partially restoring the lack of lateral roots in dgt mutant rootstocks [89]. A DGT-like small cyclophilin from Physcomitrella patens is also important for auxin-regulated growth [90], whereas a related cyclophilin from rice (LATERAL ROOTLESS2, LRT2/OsCYP2) plays a crucial role in auxin-regulated lateral root formation [91] and has been shown to directly regulate the stability of the auxin-responsive transcriptional repressor protein, OsIAA11, via peptidylprolyl isomerization [92]. The Arabidopsis cyclophilin CYCLOPHILIN20-2 regulates flowering time by modulating the conformation of BRASSINAZOLE-RESISTANT1 in Ref.…”

Peptidyl-prolyl isomerization targets rice Aux/IAAs for proteasomal degradation during auxin signalling

“…Gly 72 is a highly conserved residue located in the PPIase domain ( Supplementary Fig. 6a) and mutations in this residue of rice LRT2/OsCYP2 and moss PpDGT cause severely impaired auxin signalling 17,30 . Homologous structure modelling based on the crystal structure of wheat (Triticum aestivum) TaCypA-1 (PDB code: 4E1Q) 34 , a cyclophilin sharing 87% identity with LRT2, revealed that Gly 72 is located at the surface of LRT2 immediately adjacent to a b-sheet ( Supplementary Fig.…”

“…Mutations in the rice LATERAL ROOTLESS2 (LRT2; also known as Oryza sativa CYCLOPHILIN2 or OsCYP2) gene cause an auxin-resistant phenotype and defective development of lateral roots 16,17 . LRT2 encodes a putative cyclophilin-type peptidyl-prolyl cis/trans isomerase (PPIase) that catalyses the isomerization of peptide bonds at proline residues to specifically regulate protein conformational changes.…”

“…Previous studies showed that mutations in the rice LRT2/OsCYP2 gene (referred to as LRT2 hereafter) cause an auxin-resistant phenotype and defective development of lateral roots 16,17 . LRT2 encodes a putative cyclophilin-type PPIase that catalyses the isomerization of peptide bonds at Pro residues.…”

“…1). In particular, mutations in LRT2, OsIAA11, OsIAA13 and OsIAA23 all cause defective lateral root primordia, reduced tillering and plant height, and impaired panicle development, accompanying with the reduced expression level of auxininducible genes and the altered expression pattern of the DR5:GUS reporter gene 16,17,[31][32][33] , suggesting that LRT2 may directly target OsAux/IAAs.…”