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ABSTRACT. Patched domain-containing genes are members of a small family originally identified in Drosophila. A common feature of transmembrane patched domain-containing proteins is their function in the transport of sterols, sterol-modified proteins, and lipids. Recently, an expansion phenomenon of patched domain-containing genes was found in Caenorhabditis elegans; the major contributor to this higher number was patched-related (PTR) type genes. However, little is known about their expansion pattern and evolutionary origin. We performed a systematic genome-wide survey of patched domain-containing genes in species ranging from protozoa to vertebrates, as well as some plants. We found that patched domain-containing genes are conserved in plant and animal genomes and their expansion likely occurred in the early stages of nematode speciation. Based on analysis of phylogenetic and reconciled trees and calculation of synonymous substitutions, we discovered that the PTR genes appear to have experienced two expansions within a relatively short period after the speciation of nematodes. We also found that some patched domain-containing genes possessing a relatively 7319 Evolutionary pattern of patched domain-containing genes ©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 13 (3): 7318-7331 (2014) recent evolutionary origin, such as PTR and PTCHD1, had fewer exons and shorter nucleotide coding sequence lengths compared with the older ones. It appears that the different types of patched domain-containing genes have different evolutionary patterns in different species.

Summary Salt stress significantly induces accumulation of misfolded or unfolded proteins in plants. Endoplasmic reticulum (ER)‐associated protein degradation (ERAD) and other degradative machineries function in the degradation of these abnormal proteins, leading to enhanced salt tolerance in plants. Here we characterise that a novel receptor‐like kinase, Salt‐Induced Malectin‐like domain‐containing Protein1 (SIMP1), elevates ERAD efficiency during salt stress through UMP1A, a putative proteasome maturation factor in Arabidopsis. SIMP1 loss‐of‐function caused a salt‐hypersensitive phenotype. SIMP1 interacts and phosphorylates UMP1A, and the protein stability of UMP1A is positively regulated by SIMP1. SIMP1 modulates the 26S proteasome maturation possibly through enhancing the recruitment of specific β subunits of the core catalytic particle to UMP1A. Functionally, the SIMP1–UMP1A module plays a positive role in ERAD efficiency in Arabidopsis. The degradation of misfolded/unfolded proteins was impaired in both simp1 and ump1a mutants during salt stress. Consistently, both simp1 and ump1a plants exhibited reduced ER stress tolerance. Phenotypic analysis revealed that SIMP1 regulates salt tolerance through UMP1A at least in part. Taken together, our work demonstrated that SIMP1 modulates plant salt tolerance by promoting proteasome maturation via UMP1A, therefore mitigating ER stress through enhanced ERAD efficiency under saline conditions.

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