The genome of the seagrass <i>Zostera marina</i> reveals angiosperm adaptation to the sea

Seagrasses colonized the sea on at least three independent occasions to form the basis of one of the most productive and widespread coastal ecosystems on the planet. Here we report the genome of Zostera marina (L.), the first, to our knowledge, marine angiosperm to be fully sequenced. This reveals unique insights into the genomic losses and gains involved in achieving the structural and physiological adaptations required for its marine lifestyle, arguably the most severe habitat shift ever accomplished by flowering plants. Key angiosperm innovations that were lost include the entire repertoire of stomatal genes, genes involved in the synthesis of terpenoids and ethylene signalling, and genes for ultraviolet protection and phytochromes for far-red sensing. Seagrasses have also regained functions enabling them to adjust to full salinity. Their cell walls contain all of the polysaccharides typical of land plants, but also contain polyanionic, low-methylated pectins and sulfated galactans, a feature shared with the cell walls of all macroalgae and that is important for ion homoeostasis, nutrient uptake and O2/CO2 exchange through leaf epidermal cells. The Z. marina genome resource will markedly advance a wide range of functional ecological studies from adaptation of marine ecosystems under climate warming, to unravelling the mechanisms of osmoregulation under high salinities that may further inform our understanding of the evolution of salt tolerance in crop plants

The ovary learns to ovulate

Sensory stimuli from the external environment (e.g. visual and olfactory stimuli, stress) or internal stimuli cause brain nerve fibres to release neurotransmitters (catecholamines, indolamines and cholinergic agents). These neurotransmitters regulate the secretion of gonadotrophin-releasing hormone (GnRH) from neurosecretory cells of the hypothalamus (Kamberi, 1975). It would seem that under the proper steroid environment, catecholamines (dopamine, norepinephrine or epinephrine) and the cholinergic agent acetylcholine exert a stimulatory influence, whereas indolamines (serotonin or its metabolic product, melatonin) have an opposite effect. In turn, GnRH reaches the anterior pituitary via the hypophyseal portal system, and, through the mediation of cAMP [though may be not as an obligatory intermediate (Naor et al., 1975)], controls gonadotrophin secretion (Labrie et al., 1974

Recent radiation of the Palmariaceae (rhodophyta)

Molecular phylogenetic studies on the evolution of the red algae indicate that this ancient division has many lineages that have recently undergone radiations. One such example is the cold-temperate family Palmariaceae. In this study, sequences from the ribosomal DNA internal transcribed spacer regions were compared among ten species in the Palmariaceae from both Atlantic and Pacific sites. Phylogenetic analyses of sequence data, in which Rhodophysema georgii Batters was used as outgroup and root, indicate a radiation into four clades, three of which contain species of ''Palmaria'' and the fourth species of Halosaccion. Palmaria palmata (L.) Kuntze, the type and only North Atlantic species in the genus, stands apart from all remaining species in the family and terminates the most basal branch in the rooted tree. The three more derived clades have radiated mainly in the North Pacific. Southern Ocean Palmaria and North Atlantic Devaleraea are hypothesized to have invaded from separate but closely related North Pacific ancestors. The ease with which sequences could be aligned combined with an unsaturated transition: transversion ratio and modest divergence involving predominantly point mutations suggests that the initial radiation is relatively recent (late Miocene-Pliocene) and that the Devaleraea-Palmaria clade is even more recent (late Pliocene-Pleistocene)

Microsatellite loci in eelgrass Zostera marina reveal marked polymorphism within and among populations

Using an enriched genomic library, we developed seven (CT)(n)/(GA)(n) microsatellite loci for eelgrass Zostera marina L. Enrichment is described and highly recommended for genomes in which microsatellites are rare, such as in many plants. A test for polymorphism was performed on individuals from three geographically separated populations (N = 15/population) and revealed considerable genetic variation. The number of alleles per locus varied between five and 11 and the observed heterozygosities for single loci ranged from 0.16 to 0.81 within populations. Mean allele lengths were markedly different among populations, indicating that the identified loci will be useful in studying population structure in Z. marina. As the frequency of the most abundant multilocus genotype within populations was always <1%, these loci have sufficient resolving power to address clone size in predominantly vegetatively reproducing populations

Genetic variability and spatial separation in the sea palm kelp Postelsia palmaeformis (Phaeophyceae) as assessed with M13 fingerprints and RAPDS

Postelsia palmaeformis Ruprecht is an annual species, occuring from southern California to Vancouver Island Canada, in upper intertidal sites exposed to extreme wave shock. Because of its limited spore dispersal, discrete and inbred populations are likely on the local scale, yet dispersal of drifting and fertile thalli raises the possibility of outbred populations on a regional scale. M13 minisatellite DNA fingerprinting and random amplified polymorphic DNA (RAPD) markers were used in a complementary fashion to investigate genetic variability among 24 individuals on scales of clusters (= coalesced holdfasts)

Postglacial recolonization and the biogeography of Palmaria mollis (Rhodophyta) along the Northeast Pacific coast

We used random amplified polymorphic DNA (RAPD) markers to examine the distribution of genotypes of Palmaria mollis (Setchell et Gardner) van der Meer et Bird, a red alga. We sampled populations along the Northeast Pacific coast from northern Washington to southwestern Alaska, an area extensively glaciated during the last ice age. Our objective was to determine whether the tracks of postglacial recolonization could be extracted from the extant pattern of genotype distribution in a species with limited dispersal capabilities. Thirty-eight individuals from 14 sites were sampled for RAPD markers using nine different random primers. As expected, individuals from the same population were more closely related to each other than to individuals from other populations. Relationships among populations, however, did not necessarily reflect geographic proximity. Rather, populations fell into groups corresponding approximately to outer and inner coastal sites: the northwestern end of Vancouver Island and the Queen Charlotte Islands formed one outer coast group, which associated with sites from Prince William Sound, the Alaska Peninsula, and Sitka, Alaska; the eastern side of Vancouver Island and Ketchikan, Alaska, represented one group of inner sites, which associated with sites near Juneau, Alaska and the eastern end of the Strait of Juan de Fuca. We conclude that this pattern does not represent a single postglacial recolonization event