Levels of 20S and 26S proteasomes are regulated by Arabidopsis plant-specific NAC transcription factor, ANAC078

Abstract

Recently we have reported that the transcription of 166 genes in ANAC078-overexpressing Arabidopsis plants (Ox-ANAC078) was up-regulated compared with the levels in wild-type plants under high-lihgt (HL) (Plant Cell Physiol., 2009). Interestingly, these genes included 13 members of the proteasome subunit genes. These findings suggest that the levels of proteasome are regulated by ANAC078. To explore the gene regulatory system of proteasome subunit genes via ANAC078 under stressful conditions, the transcript levels of proteasome subunit genes in response to HL stress (1200 μmol/m²/s) were analyzed. The transcript levels of several proteasome subunit genes in the Ox-ANAC078 plants were higher than those in the wild-type plants under normal conditions and HL stress. Furthermore, the levels of 26S and 20S proteasomes and chymotrypsin-like activity were highly increased in the Ox-ANAC078 plants compared with those in the wild-type plants. These data indicated that ANAC078 regulates the levels of 20S and 26S proteasomes under stressful conditions.