Identification and evolution of C4 photosynthetic pathway genes in plants.

BACKGROUND: NADP-malic enzyme (NAPD-ME), and pyruvate orthophosphate dikinase (PPDK) are important enzymes that participate in C4 photosynthesis. However, the evolutionary history and forces driving evolution of these genes in C4 plants are not completely understood. RESULTS: We identified 162 NADP-ME and 35 PPDK genes in 25 species and constructed respective phylogenetic trees. We classified NADP-ME genes into four branches, A1, A2, B1 and B2, whereas PPDK was classified into two branches in which monocots were in branch I and dicots were in branch II. Analyses of selective pressure on the NAPD-ME and PPDK gene families identified four positively selected sites, including 94H and 196H in the a5 branch of NADP-ME, and 95A and 559E in the e branch of PPDK at posterior probability thresholds of 95%. The positively selected sites were located in the helix and sheet regions. Quantitative RT-PCR (qRT-PCR) analyses revealed that expression levels of 6 NADP-ME and 2 PPDK genes from foxtail millet were up-regulated after exposure to light. CONCLUSION: This study revealed that positively selected sites of NADP-ME and PPDK evolution in C4 plants. It provides information on the classification and positive selection of plant NADP-ME and PPDK genes, and the results should be useful in further research on the evolutionary history of C4 plants.

Passive origins of stomatal control in vascular plants.

Carbon and water flow between plants and the atmosphere is regulated by the opening and closing of minute stomatal pores in surfaces of leaves. By changing the aperture of stomata, plants regulate water loss and photosynthetic carbon gain in response to many environmental stimuli, but stomatal movements cannot yet be reliably predicted. We found that the complexity that characterizes stomatal control in seed plants is absent in early-diverging vascular plant lineages. Lycophyte and fern stomata are shown to lack key responses to abscisic acid and epidermal cell turgor, making their behavior highly predictable. These results indicate that a fundamental transition from passive to active metabolic control of plant water balance occurred after the divergence of ferns about 360 million years ago.

[Distribution of a betaine lipid O-(1,2-diacylglycero)-N,N,N-trimethylhomoserine in tissues of some Lycopodiophyta species]. / Raspredelenie betainovogo lipida O-(1,2-diatsilglitsero)-N,N,N-trimetilgomoserina v tkaniakh nekotorykh vidov Lycopodiophyta.

The distribution of O-(1,2-diacylglycero)-4'-(N,N,N-trimethyl)homoserine (DGTS), a betaine lipid, in ten samples of plants belonging to the division Lycopodiophyta collected in various habitats was studied. Homogeneous plant tissues (vegetative shoots and spikelets) and mixed tissues (shoots with spikelets) were analyzed. Particular attention was paid to the DGTS-synthesizing ability of various club mosses and to various tissue types forming an organ in a single plant species, as well as the ratio between DGTS and other glycerolipid classes. The English version of the paper: Russian Journal of Bioorganic Chemistry, 2004, vol. 30, no. 6; see also http://www.maik.ru.

Occurrence of the primary cell wall polysaccharide rhamnogalacturonan II in pteridophytes, lycophytes, and bryophytes. Implications for the evolution of vascular plants.

Borate ester cross-linking of the cell wall pectic polysaccharide rhamnogalacturonan II (RG-II) is required for the growth and development of angiosperms and gymnosperms. Here, we report that the amounts of borate cross-linked RG-II present in the sporophyte primary walls of members of the most primitive extant vascular plant groups (Lycopsida, Filicopsida, Equisetopsida, and Psilopsida) are comparable with the amounts of RG-II in the primary walls of angiosperms. By contrast, the gametophyte generation of members of the avascular bryophytes (Bryopsida, Hepaticopsida, and Anthocerotopsida) have primary walls that contain small amounts (approximately 1% of the amounts of RG-II present in angiosperm walls) of an RG-II-like polysaccharide. The glycosyl sequence of RG-II is conserved in vascular plants, but these RG-IIs are not identical because the non-reducing L-rhamnosyl residue present on the aceric acid-containing side chain of RG-II of all previously studied plants is replaced by a 3-O-methyl rhamnosyl residue in the RG-IIs isolated from Lycopodium tristachyum, Ceratopteris thalictroides, Platycerium bifurcatum, and Psilotum nudum. Our data indicate that the amount of RG-II incorporated into the walls of plants increased during the evolution of vascular plants from their bryophyte-like ancestors. Thus, the acquisition of a boron-dependent growth habit may be correlated with the ability of vascular plants to maintain upright growth and to form lignified secondary walls. The conserved structures of pteridophyte, lycophyte, and angiosperm RG-IIs suggests that the genes and proteins responsible for the biosynthesis of this polysaccharide appeared early in land plant evolution and that RG-II has a fundamental role in wall structure.