Developmental and Light-Regulated Expression of Individual Members of the Light-Harvesting Complex b Gene Family in Pinus palustris

Abstract

Angiosperms require light for multiple aspects of chloroplast development, including chlorophyll synthesis and induction of expression of the mRNAs encoding the major polypeptides of the light-harvesting complex of photosystem I1 (Lhcb genes). I n contrast, many conifers, including pines, firs, and spruces, can accumulate chlorophyll and the light-harvesting chlorophyll a/b-binding proteins of photosystem II in complete darkness. To understand the factors responsible for the regulation of expression of individual Lhcb mRNAs in the pine Pinus palustris, we have prepared sequence-specific cDNA probes for each of three family members, Lhcbf'Ppl, Lhcb2*Ppl, and Lhcb2*Pp2, and have studied the expression of two of these, Lhcbl'Ppl and Lhcb2*Pp2, in detail. The levels of expression of each sequence were disparate, and Lhcbl'Ppl-encoded transcripts were the most abundant i n the light. Both Lhcbl*Ppl and Lhcb2'PpZ mRNAs were expressed i n stems and cotyledons, but Lhcbl'Ppl mRNA was present at about 10-fold lower levels in stems than in cotyledons, i n contrast to Lhcb2*Pp2 mRNA, which was expressed at higher levels in stems than i n cotyledons. Both Lhcbl*Ppl and Lhcb2*Pp2 mRNAs were absent in embryos but were expressed during seedling development. The levels increased with age in both the light and the dark and in both cases were about 2-fold higher i n the light than in the dark. Despite the expression of Lhcbl'Ppl and Lhcb2*Pp2 mRNAs during development in darkness, the levels of both mRNAs increased in dark-grown seedlings given red light i n the low fluence range within 2 h of treatment.Photosynthesis in higher plants is carried out in two photosystems, termed I' S1 and PSII, which are located in the thylakoid membranes of the chloroplast (reviewed by Grossman et al., 1995). Light energy for the photosynthetic reactions is collected by the LHCs associated with each photosystem (LHCI or LHCII). Each LHC comprises an aggregate of polypeptides specific for each photosystem noncovalently bound to a characteristic group of chloro-

Molecular characterization of 5-chlorophyll a/b-binding protein genes from Panax ginseng Meyer and their expression analysis during abiotic stresses

“…4), showing difference with expression pattern in four-week-old leaves, could be explained by regulation during development (Bassett et al 2003, Xu et al 2012. It is well established that light is the most important environmental signal to regulate Lhc expression (Silverthorne and Tobin 1984, Sun and Tobin 1990, Millar and Kay 1996, Peer et al 1996, Weatherwax et al 1996, Yang et al 1998, Humbeck and Krupinska 2003, Staneloni et al 2008, De Montaigu et al 2010, Pruneda-Paz and Kay 2010, Thines and Harmon 2010. Corresponding with dark-dependent inhibition of CAB expression (Matsuoka 1990), the five PgCABs showed very low expression level in dark condition (Fig.…”

Clock genes and diurnal transcriptome dynamics in summer and winter in the gymnosperm Japanese cedar ( Cryptomeria japonica (L.f.) D.Don)

“…Lhcb and psbA (photosystem II subunit A) mRNA levels show only small diurnal fluctuations under light/dark cycles and no circadian rhythm under continuous light or dark conditions in Douglas fir (Pseudotsuga menziesii) [65]. By analyzing dark-grown seedlings, expression of Lhcb genes has been shown to occur in darkness in various conifer species [64][65][66][67][68][69]. Expression of PHYA/C-related genes in dark-grown P. abies seedlings has also been reported [69].…”

Evolution of Light-Regulated Plant Promoters

“…Asterisks denote mismatches between aligned sequences. well established in conifers (4,71,89,94,137), although to our knowledge, no detailed molecular studies have been carried out in pteridophytas and bryophytas. Conifers and other nonflowering plants (Gingko biloba being an exception; 24, 25) develop chloroplasts when grown in darkness (83,129,130), indicating that their PhANG promoters are active in the dark.…”