Characterization of Amaranthus hypochondriacus light-harvesting chlorophyll a/b-binding polypeptide cDNAs.

Abstract

The Lhcp constituents of the photosynthetic apparatus of higher plants form protein-pigment complexes that are involved in the capture and distribution of light energy in both photosystems in the thylakoid membranes (Anderson, 1986). Severa1 Lhcps encoded by multigene families and closely related on a structural basis are found in each plant species (Buetow et al., 1988). Sequences for Lhcp genes isolated from C4 monocotyledonous plants such as maize (Viret et al., 1990) have been reported previously. Here we report the sequence and characterization of two cDNA clones of the C4 dicotyledonous plant Amaranthus hypochondriachus (Table I). The two Lhcp Amaranth clones show varying degrees of homology (44-60% when coding sequences are compared) with other Lhcp clones found in the GenBank data base. Lhcb2*Ahl is 11 16 bp long and corresponds to a full-length Lhcp mRNA, which has a putative untranslated leader sequence of 169 bp and a 3' untranslated region of 152 bp. The deduced amino acid sequence for this clone corresponds to a 264-amino acid protein, 35 amino acids making up the transit peptide and 229 making up the mature polypeptide. LhcbZ*Ahl shows strong (>75%) homology to the deduced amino acid sequences corresponding to PSII type I1 genes from other species. In addition, the transit peptide also corresponds to PSII type I1 sequences. Lhcbl*Ahl is a 5' truncated clone, 679 bp in length, comprising a putative coding region corresponding to a 180amino acid polypeptide and a 3' untranslated region of 121 bp. The degree of homology of Lhcbl*Ahl (>60% at the nucleotide level) with PSII type I sequences of other species suggests that this gene is of this type. The Amaranthus cDNAs have 79% homology at the nucleotide sequence level and differ in 22 amino acids in the deduced amino acid sequences. The octanucleotide sequence, GGAGAAAA, is the only common feature of the 3' untranslated region of both cDNA '