Analysis of Porphyra Membrane Transporters Demonstrates Gene Transfer among Photosynthetic Eukaryotes and Numerous Sodium-Coupled Transport Systems      

Abstract

Membrane transporters play a central role in many cellular processes that rely on the movement of ions and organic molecules between the environment and the cell, and between cellular compartments. Transporters have been well characterized in plants and green algae, but little is known about transporters or their evolutionary histories in the red algae. Here we examined 482 expressed sequence tag contigs that encode putative membrane transporters in the economically important red seaweed Porphyra (Bangiophyceae, Rhodophyta). These contigs are part of a comprehensive transcriptome dataset from Porphyra umbilicalis and Porphyra purpurea. Using phylogenomics, we identified 30 trees that support the expected monophyly of red and green algae/plants (i.e. the Plantae hypothesis) and 19 expressed sequence tag contigs that show evidence of endosymbiotic/horizontal gene transfer involving stramenopiles. The majority (77%) of analyzed contigs encode transporters with unresolved phylogenies, demonstrating the difficulty in resolving the evolutionary history of genes. We observed molecular features of many sodium-coupled transport systems in marine algae, and the potential for coregulation of Porphyra transporter genes that are associated with fatty acid biosynthesis and intracellular lipid trafficking. Although both the tissue-specific and subcellular locations of the encoded proteins require further investigation, our study provides red algal gene candidates associated with transport functions and novel insights into the biology and evolution of these transporters.

Metatranscriptome profiling reveals versatile N-nutrient utilization, CO2 limitation, oxidative stress, and active toxin production in an Alexandrium fundyense bloom

“…Another abundant gene is aquaporin (also known as water channel proteins), which is critical for osmotic regulation and transportation of other small polar molecules across membranes (Maurel, 1997). We detected a total of 15 aquaporin-coding unigenes in A. fundyense while previous studies detected 1-6 in chlorophytes (Anderberg et al, 2011), 2-3 in Porphyra species (Chan et al, 2012). Plants possess 23-37 aquaporin paralogs (Anderberg et al, 2011) and aquaporins in Arabidopsis have been characterized to transport urea and ammonia besides water (Soto et al, 2008(Soto et al, , 2010.…”

“…Remarkably, we found 13 distinct unigenes of NH 4 + transporters, the highest number among the algae studied so far. Two to nine NH 4 + transporters have been described in the completely sequenced genomes of microalgae, while 7 and 10 were reported in the EST datasets of two multicellular rhodophyte Porphyra species, respectively (Chan et al, 2012). Another abundant gene is aquaporin (also known as water channel proteins), which is critical for osmotic regulation and transportation of other small polar molecules across membranes (Maurel, 1997).…”

Transcriptomic analysis of the red seaweed Laurencia dendroidea (Florideophyceae, Rhodophyta) and its microbiome

“…Moreover, EST projects have provided valuable information in the transcriptomic profile of some species of Rhodophyta [50,51,58-62] in the phylogenetic relationships among photosynthetic eukaryotes [63,64] and have also unveiled genes involved in stress response [52,65,66] and in life phase differentiation [67-70]. …”

Structural divergence and loss of phosphoinositide-specific phospholipase C signaling components during the evolution of the green plant lineage: implications from structural characteristics of algal components

“…In addition, large-scale EST information has been accumulated for the red seaweeds Porphyra umbilicalis and Porphyra purpurea (Chan et al, 2012; Stiller et al, 2012). Because understanding the evolutionary aspects of PtdIns signaling can help us to understand the process of establishment of the plant PtdIns signaling system, algal PI-PLC and PIPK protein structures have been compared with those of terrestrial plants.…”