6533b837fe1ef96bd12a339f

RESEARCH PRODUCT

Cryptogein affects expression of alpha3, alpha6 and beta1 20S proteasome subunits encoding genes in tobacco.

subject

description

Twelve a and b 20S proteasome subunits cDNAs showing 70–82% identity with the corresponding genes in Arabidopsis or rice, and features of eukaryotic proteasome subunits were cloned in tobacco. Only b1-tcI 7, a3 and a6, 20S proteasome subunits encoding genes were up-regulated by cryptogein, a proteinaceous elicitor of plant defence reactions. These results led to the hypothesis that the activation of b1-tcI 7, a3 and a6 could induce a specific proteolysis involved in the hypersensitive response and systemic acquired resistance monitored by cryptogein. In eukaryotes, the 26S proteasome is the central multicatalytic proteinase complex comprising two subcomplexes: the 20S core particle that performs proteolysis and the 19S regulatory particle that recognizes the protein targeted for degradation. The 20S proteasome is a stack of four seven-membered rings, the two outer rings being formed by seven a subunits and the two inner rings by seven b subunits. The central b rings enclose a cavity that houses the active sites allowing the progressive degradation of proteins. In mammals, proteasomes are shown to be involved in the degradation of misfolded proteins and also in biological functions such as cell cycle progression or cell death, and specific proteolysis such as the cleavage of propeptides in order to activate peptides