Chloroplast Biogenesis 77: Two Novel Monovinyl and Divinyl Light‐Dark Greening Groups of Plants and Their Relationship to the Chlorophyll a Biosynthetic Heterogeneity of Green Plants

Abstract

Abstract— On the basis of the steady‐state accumulation of divinyl (DV) or monovinyl (MV) protochlorophyllide (Pchlide) a in darkness (D) or in the light (L), green plants have been classified into three different greening groups namely dark divinyl‐light divinyl (DDV‐LDV), dark monovinyl‐light divinyl (DMV‐LDV) and dark monovinyl‐light monovinyl (DMV‐LMV) (Ionannides et al., Biochem. Syst. Ecol. 22, 211‐220,1994). Interruption of the L phase of the photoperiod by a brief period of darkness (LD condition) revealed a predominance of different chlorophyll (Chl) a biosynthetic routes, depending upon the greening group affiliation of the plant species. For example, in DMV‐LDV and DMV‐LMV plants, the predominant Chl a biosynthetic routes under the LD condition appear to be the MV Chi a biosynthetic route and/or a mixed DV‐MV Chi a biosynthetic route that bifurcates at the level of DV Pchlide a. On the basis of DV and MV Pchlide a accumulation rates after re‐darkening, this greening group is designated as a light‐dark MV (LDMV) subgroup. In DDV‐LDV plants, the predominant LD Chi a biosynthetic routes appear to be the DV Chi a biosynthetic route and/or a mixed DV‐MV Chi a biosynthetic route that bifurcates at the level of DV Chlide a. This greening group is designated as a light‐dark DV (LDDV) subgroup. It is proposed that upon inhibiting the conversion of Pchlide a to Chi a by interruption of the L phase of the photoperiod by a brief period of D, the rates of DV and MV Pchlide a regeneration may reflect the carryover rates of DV and MV Pchlide a biosynthesis in L instead of reflecting a differential use of DV and MV carboxylic biosynthetic rates in D. It is also shown that in LDMV plants, MV Chlide a and MV Chi a are formed without the participation of [4‐vinyl] Chlide a reductase. On the basis of recently published evidence, it is also argued that Pchlide oxidoreductase‐A (POR‐A) may be active in LDDV plants, while POR‐B may predominate in LDMV plant species. The evolutionary significance of the LDDV and LDMV greening subgroups is discussed.