AKR-deficiency disturbs the balance of some signal transduction pathways in Arabidopsis thaliana

High-intensity light induces anthocyanin production in wild-type Arabidopsi s leaves, but this induction is largely abolished in the chlorotic leaf tis sues of AKR (ankyrin repeat-containing protein)-deficient plants. The stead y-state mRNA levels of three anthocyanin biosynthetic genes, CHI, CHS and D FR, did not increase in response to high-intensity light treatment in chlor otic leaf tissues, whereas they increased several fold in green leaf tissue s. There is a good correlation between anthocyanin production and transcrip t levels of anthocyanin biosynthetic genes, especially DFR, in green leaf t issues. In contrast, the transcripts of TCH2 and TCH3 that encode for calmo dulin-related proteins and GPA that encodes for the a subunit of the trimer ic G protein were much higher in chlorotic leaf tissues than those in green leaf tissues. These data suggest that the AKR-deficiency could increase ge ne expression in one signal transduction pathway and at the same time repre ss gene expression in another signal transduction pathway, which alludes to a possible mechanism for AKR involvement in chloroplast development. (C) E lsevier, Paris.