Cycas
Gymnosperms
Evidence for long isolation among populations of a pacific cycad: genetic diversity and differentiation in Cycas seemannii A.Br. (Cycadaceae). (1/25)
The genetic structure of Cycas seemannii A.Br. (Cycadaceae), sampled throughout its range in Vanuatu, New Caledonia, Fiji, and Tonga, was studied using starch-gel electrophoresis. Twenty enzyme loci in 13 enzyme systems were examined. Low genetic diversity within populations (A = 1.2, P = 21.3, Ho = 0.047, and He = 0.057) and a high degree of differentiation among populations (F(ST) = 0.594) were found. This, together with low gene flow estimates, suggests genetic drift by isolation to have been most critical to the current genetic structure of the species. Inbreeding may occur to some extent (F(IS) = 0.165). The decline in abundance of C. seemannii, coupled with the low level of genetic diversity, suggest that conservation strategies are urgently needed. (+info)Biomagnification of cyanobacterial neurotoxins and neurodegenerative disease among the Chamorro people of Guam. (2/25)
We here report biomagnification (the increasing accumulation of bioactive, often deleterious molecules through higher trophic levels of a food chain) of the neurotoxic nonprotein amino acid beta-methylamino-l-alanine (BMAA) in the Guam ecosystem. Free-living cyanobacteria produce 0.3 microg/g BMAA, but produce 2-37 microg/g as symbionts in the coralloid roots of cycad trees. BMAA is concentrated in the developing reproductive tissues of the cycad Cycas micronesica, averaging 9 microg/g in the fleshy seed sarcotesta and a mean of 1,161 microg/g BMAA in the outermost seed layer. Flying foxes (Pteropus mariannus), which forage on the seeds, accumulate a mean of 3,556 microg/g BMAA. Flying foxes are a prized food item of the indigenous Chamorro people who boil them in coconut cream and eat them whole. Chamorros who die of amyotrophic lateral sclerosis/parkinsonism-dementia complex (AL-SPDC), a neurodegenerative disease with symptoms similar to amyotrophic lateral sclerosis, Parkinson's disease, and Alzheimer's disease, have an average of 6.6 microg/g BMAA in their brain tissues. The biomagnification of BMAA through the Guam ecosystem fits a classic triangle of increasing concentrations of toxic compounds up the food chain. This may explain why the incidence of ALS-PDC among the Chamorro was 50-100 times the incidence of amyotrophic lateral sclerosis elsewhere. Biomagnification of cyanobacterial BMAA may not be unique to Guam; our discovery of BMAA in the brain tissue from Alzheimer's patients from Canada suggests alternative ecological pathways for the bioaccumulation of BMAA in aquatic or terrestrial ecosystems. (+info)Expressed sequence tag analysis in Cycas, the most primitive living seed plant. (3/25)
BACKGROUND: Cycads are ancient seed plants (living fossils) with origins in the Paleozoic. Cycads are sometimes considered a 'missing link' as they exhibit characteristics intermediate between vascular non-seed plants and the more derived seed plants. Cycads have also been implicated as the source of 'Guam's dementia', possibly due to the production of S(+)-beta-methyl-alpha, beta-diaminopropionic acid (BMAA), which is an agonist of animal glutamate receptors. RESULTS: A total of 4,200 expressed sequence tags (ESTs) were created from Cycas rumphii and clustered into 2,458 contigs, of which 1,764 had low-stringency BLAST similarity to other plant genes. Among those cycad contigs with similarity to plant genes, 1,718 cycad 'hits' are to angiosperms, 1,310 match genes in gymnosperms and 734 match lower (non-seed) plants. Forty-six contigs were found that matched only genes in lower plants and gymnosperms. Upon obtaining the complete sequence from the clones of 37/46 contigs, 14 still matched only gymnosperms. Among those cycad contigs common to higher plants, ESTs were discovered that correspond to those involved in development and signaling in present-day flowering plants. We purified a cycad EST for a glutamate receptor (GLR)-like gene, as well as ESTs potentially involved in the synthesis of the GLR agonist BMAA. CONCLUSIONS: Analysis of cycad ESTs has uncovered conserved and potentially novel genes. Furthermore, the presence of a glutamate receptor agonist, as well as a glutamate receptor-like gene in cycads, supports the hypothesis that such neuroactive plant products are not merely herbivore deterrents but may also serve a role in plant signaling. (+info)ISSR variation in the endemic and endangered plant Cycas guizhouensis (Cycadaceae). (4/25)
BACKGROUND AND AIMS: Cycas guizhouensis (Cycadaceae) is a rare and endangered species endemic to the southwest of China. An investigation was undertaken into the genetic variation of wild populations. METHODS: ISSR markers were used to determine the genetic variation within and between 12 extant populations of this species. KEY RESULTS: Low genetic diversity (at population level, P = 14.21 %, H(E) = 0.0597; at species level, P = 35.90 %, H(T) = 0.1082) and a high degree of differentiation among populations (G(ST) = 0.4321) were detected. CONCLUSIONS: This genetic structure is considered to be due to the combined effects of slow biochemical evolution, genetic drift, inbreeding and limited gene flow between populations. Based on these findings, strategies are proposed for the genetic conservation and management of the species. (+info)A mechanism for slow release of biomagnified cyanobacterial neurotoxins and neurodegenerative disease in Guam. (5/25)
As root symbionts of cycad trees, cyanobacteria of the genus Nostoc produce beta-methylamino-l-alanine (BMAA), a neurotoxic nonprotein amino acid. The biomagnification of BMAA through the Guam ecosystem fits a classic triangle of increasing concentrations of toxic compounds up the food chain. However, because BMAA is polar and nonlipophilic, a mechanism for its biomagnification through increasing trophic levels has been unclear. We report that BMAA occurs not only as a free amino acid in the Guam ecosystem but also can be released from a bound form by acid hydrolysis. After first removing free amino acids from tissue samples of various trophic levels (cyanobacteria, root symbioses, cycad seeds, cycad flour, flying foxes eaten by the Chamorro people, and brain tissues of Chamorros who died from amyotrophic lateral sclerosis/Parkinsonism dementia complex), we then hydrolyzed the remaining fraction and found BMAA concentrations increased 10- to 240-fold. This bound form of BMAA may function as an endogenous neurotoxic reservoir, accumulating and being transported between trophic levels and subsequently being released during digestion and protein metabolism. Within brain tissues, the endogenous neurotoxic reservoir can slowly release free BMAA, thereby causing incipient and recurrent neurological damage over years or even decades, which may explain the observed long latency period for neurological disease onset among the Chamorro people. The presence of BMAA in brain tissues from Canadian patients who died of Alzheimer's disease suggests that exposure to cyanobacterial neurotoxins occurs outside of Guam. (+info)Biflavonoids from Cycas beddomei. (6/25)
Chemical investigation on the constituents of the cones of Cycas beddomei has resulted in the isolation of a new biflavonoid, 2,3-dihydro-4'''-O-methyl amentoflavone, along with 2,3,2'',3''-tetrahydro hinokiflavone, 2,3,2'',3''-tetrahydro amentoflavone, 2,3-dihydro amentoflavone. The last two compounds were not reported earlier from this plant. The structure of the new compound was established by detailed analysis of its spectral (mainly 1D and 2D NMR) data. (+info)Genetic differentiation and relationships of populations in the Cycas balansae complex (Cycadaceae) and its conservation implications. (7/25)
BACKGROUND AND AIMS: The Cycas balansae complex is arguably a controversial group with regard to species delineation. Some taxonomists recognize a single polymorphic species while others distinguish five narrowly defined ones. The unresolved taxonomy has the potential to bring about significant problems for species conservation. Thus, an investigation to examine the genetic diversity and differentiation in the C. balansae complex was performed to determine the relationship of populations and to test whether the morphologically defined segregations represent genetically distinct units. METHODS: Inter-simple sequence repeat (ISSR) markers were employed to assess the genetic diversity in the C. balansae complex with a sample of 158 individuals from all extant populations in China. KEY RESULTS: ISSR markers revealed low genetic diversity in all populations studied (H(E) and H(O) averaged 0.0639 and 0.0798 at the population level, respectively). Phenetic analysis showed that the C. balansae complex grouped into five clusters closely corresponding to the narrowly defined C. balansae, C. parvula, C. shiwandashanica, C. tanqingii and C. simplicipinna. CONCLUSIONS: ISSR data suggest that the C. balansae complex has evolved into five genetically distinct units. These might be derived from a relatively widespread common ancestor through multiple vicariant events including geographical isolation resulting from the collision of the Indian plate with the Eurasian plate and from Pleistocene glaciations. In conservation, attention should be paid to each genetic unit. (+info)Cloning and expression of a mannose-binding jacalin-related lectin from leaves of Japanese cycad (Cycas revoluta Thunb.). (8/25)
Cycad leaf lectin (CRLL), a mannose-recognizing jacalin-related lectin (mJRL), was first cloned as a gymnosperm lectin and expressed. The cDNA sequence of CRLL (DDBJ, accession no. AB198328), coding 291 amino acid residues, has a tandem repeat of about 150 amino acids divided into N- and C-terminal domains as Japanese chestnut mJRL. Sequence alignment showed deletion and insertion of the sequence, and its putative carbohydrate-binding sites showed some differences from other JRLs. PCR analysis showed that this lectin was expressed in the cycad leaf but not in the root or seed. Recombinant CRLL (rCRLL) was expressed in Escherichia coli and purified by affinity chromatography after refolding procedures. Properties of active rCRLL appeared to be almost the same as those of native CRLL. (+info)I'm not aware of a medical definition for the term "Cycas." It is a genus name in botany, referring to a group of plants commonly known as cycads. Cycads are ancient seed plants that have been on Earth for millions of years. They are often grown as ornamental plants due to their unique appearance.
While there may not be a direct medical definition for "Cycas," it is worth noting that some parts of the cycad plant, particularly the seeds, contain toxic compounds that can cause serious health issues in both humans and animals if ingested. These toxins can affect the nervous system, liver, and kidneys, leading to symptoms such as vomiting, seizures, and even death in severe cases.
Therefore, while "Cycas" may not have a medical definition per se, it is still important to be aware of its potential health risks.
Gymnosperms are a group of seed-producing plants that include conifers, cycads, Ginkgo, and gnetophytes. The name "gymnosperm" comes from the Greek words "gymnos," meaning naked, and "sperma," meaning seed. This refers to the fact that the seeds of gymnosperms are not enclosed within an ovary or fruit, but are exposed on the surface of modified leaves called cones or strobili.
Gymnosperms are vascular plants, which means they have specialized tissues for transporting water and nutrients throughout the plant. They are also heterosporous, meaning that they produce two types of spores: male microspores and female megaspores. The microspores develop into male gametophytes, which produce sperm cells, while the megaspores develop into female gametophytes, which produce egg cells.
Gymnosperms are an important group of plants that have been around for millions of years. They are adapted to a wide range of environments, from temperate forests to deserts and high mountain ranges. Many gymnosperms are evergreen, with needle-like or scale-like leaves that are able to resist drought and cold temperatures.
Conifers, which include trees such as pines, firs, spruces, and redwoods, are the most diverse and widespread group of gymnosperms. They are characterized by their woody cones and needle-shaped leaves. Cycads are another group of gymnosperms that are found in tropical and subtropical regions. They have large, stiff leaves and produce large seeds that are enclosed in a fleshy covering. Ginkgo is a unique gymnosperm that has been around for over 200 million years. It is a deciduous tree with fan-shaped leaves and large, naked seeds.
Gnetophytes are a small group of gymnosperms that include the ephedra, welwitschia, and gnetum. They have unique features such as vessels in their wood and motile sperm cells, which are not found in other gymnosperms.
Overall, gymnosperms are an important group of plants that have adapted to a wide range of environments and play a crucial role in many ecosystems.
"Gnetum" is a botanical term that refers to a genus of plants in the family Gnetaceae. These plants are not commonly referred to as "Gnetum" in a medical context, but rather by the specific names of their edible species, such as Gnetum gnemon (called "Melinjo" in Indonesian) and Gnetum Africanum (called "Okazi" or "Ukazi" in West Africa).
The leaves, seeds, and stems of some Gnetum species are used in traditional medicine in various parts of the world. However, there is limited scientific evidence to support their medicinal uses. Therefore, it's important to consult with a healthcare professional before using any plant-based remedies for medical purposes.