MOLECULAR CHARACTERIZATION OF ARABIDOPSIS THALIANA T-DNA KNOCKOUT MUTANTS OF POR ISOZYMES (porB AND porC) ENCODING LIGHT-DEPENDENT PROTOCHLOROPHYLLIDE OXIDOREDUCTASE

Abstract

NADPH-protochlorophyllide oxidoreductase (POR) catalyses the light-dependent reduction of protochlorophyllide a. Three differentially regulated POR isoforms have isolated from Arabidopsis thaliana. To elucidate the physiological function of each POR isoform, we screened POR mutants in T-DNA tagged populations. Isolation of porB mutant has previously presented at 2001th JSPP meeting, and here we present the isolation and analysis of T-DNA knockout porC mutants. Two independent porC mutants were obtained after screening. No detectable PORC was accumulated in two mutants, indicating both mutants are null mutation of PORC. Like porB, porC seedlings grown under white light showed comparable Chl accumulation and photosynthetic activity to those of wild type. However, only porB showed higher sensitivity to the far-red block of greening response. These results suggest that PORB and PORC are functionally redundant under normal growth conditions. However, under limited environmental or developmental conditions, expression of particular POR isoforms is important for normal chloroplast development.