Ubiquitin-Specific Protease 2 (OsUBP2) Negatively Regulates Cell Death and Disease Resistance in Rice

Abstract

Lesion mimic mutants (LMMs) are great materials for studying programmed cell death and immune mechanisms in plants. Various mechanisms are involved in the phenotypes of different LMMs, but few studies have explored the mechanisms linking deubiquitination and LMMs in rice (Oryza sativa). Here, we identified a rice LMM, rust spots rice (rsr1), resulting from the mutation of a single recessive gene. This LMM has spontaneous reddish-brown spots on its leaves, and displays enhanced resistance to both fungal leaf blast (caused by Magnaporthe oryzae) and bacterial blight (caused by Xanthomonas oryzae pv. oryzae). Map-based cloning showed that the mutated gene in rsr1 encodes a Ubiquitin-Specific Protease 2 (OsUBP2). The mutation of OsUBP2 was shown to result in reactive oxygen species (ROS) accumulation, chloroplast structural defects, and programmed cell death, while the overexpression of OsUBP2 weakened rice resistance to leaf blast. OsUBP2 is therefore a negative regulator of immune processes and ROS production. OsUBP2 has deubiquitinating enzyme activity in vitro, and the enzyme active site includes a cysteine at the 234th residue. The ubiquitinated proteomics data of rsr1 and WT provide some possible target protein candidates for OsUBP2.

Genome-wide identification and expression analysis of Ubiquitin-specific protease gene family in maize (Zea mays L.)

“…A recent study showing that The UBP5 histone H2A deubiquitinase counteracts PRCs-mediated repression to regulate Arabidopsis development informs the study of the histone deubiquitination function of the homologue ZmUBP5 in maize [ 36 ]. In addition, OsUBP2 (Os09g0505100) in rice and TaUBP1A.1 in wheat were proved to be resistant to leaf blight and Chinese wheat mosaic virus (CWMV), and both belonged to group 1 [ 6 , 16 ], indicating that ZmUBP12 and ZmUBP21 belonging to group 1 subfamily may be resistant to biotic stress. In addition, UBP genes of wheat and rice were evolutionarily closer to maize UBP genes than Arabidopsis UBP genes (Fig.…”

“…Ubiquitin-specific proteases (UBPs), the largest subfamily of plant deubiquitinating enzymes (DUBs), are involved in diverse physiological processes such as plant growth and development [ 1 – 5 ], as well as stress response [ 6 – 8 ]. According to previous studies, eukaryotic DUBs can be classified into five subfamilies and two types based on their catalytic domains: cysteine proteases and metalloproteinases [ 9 , 10 ], with UBPs falling into the cysteine protease category [ 11 ].…”

“…UBP12 and UBP13 also play an important role in the regulation of plant flowering time and the biological clock of plants [ 5 ]. UBPs have been shown to play an important role in stress responses, such as the plant immune response, drought response mediated by the ABA signaling pathway, salt response and other biological processes [ 6 , 8 , 22 – 24 ].…”

An insight into the roles of ubiquitin-specific proteases in plants: development and growth, morphogenesis, and stress response

“…In rice, Osubp2 exhibits enhanced resistance to bacterial blight and leaf blast caused by Xanthomonas oryzae pv. oryzae and Magnaporthe oryzae , respectively, whereas OsUBP2 overexpression causes chloroplast structural defects, programmed cell death, and reactive oxygen species accumulation, resulting in reduced resistance to rice blast ( Jiang et al., 2022a ).…”

Genome-Wide Identification, Characterization, and Expression Analysis under Abiotic Stresses of the UBP Gene Family in Rice (Oryza sativa L.)

“…OsUBP15 directly interacts with OsDA1 and promotes the width and size of the grain [17]. OsUBP2 is a negative regulator of reactive oxygen species (ROS) accumulation and immunity [18]. Further research suggests that OsUBP2 may regulate rice cell death and immune responses by stabilizing SPL35 [19].…”