Are plants with anti-cancer activity resistant to crown gall? : A test of hypothesis

The Crown gall tumour assay (CGTA) is one of several bench top bioassays recommended for the rapid screening of plants with anti-cancer activity. The rationale for the use of the bioassay is that the tumorogenic mechanism initiated in plant tissues by _Agrobacterium tumefaciens_ is in many ways similar to that of animals. Several plant species with anti-cancer activity have already been discovered using this bioassay. However till date no explicit test of an association between anti-cancer activity of plants and their resistance to crown gall formation has been demonstrated. Demonstration of an association could have exploratory potential when searching for plants with anti-cancer activity. In this paper, we determined whether or not a statistically significant association between crown gall resistance and anti-cancer activity exists in plants found in existing published data sets. Our results indicate that plants with anti-cancer activity have a higher proportion of their species resistant to crown gall formation compared to a random selection of plants. We discuss the implications of our results especially when prospecting for newer sources of anti-cancer activity in plants

Stylish lengths: Mate choice in flowers

The styles of flowers may represent an arena for pollen competition in the race to fertilize ovules. Accordingly, selection should favour a longer 'race' to better discriminate among variable pollen by increasing style length. Sampling across a taxonomically diverse range of wild and outcrossed species, we found that the distribution of style lengths within plants were skewed towards longer styles, as predicted. In self-pollinated domesticated species, where discrimination among pollen is less important, we found no such pattern. We conclude that style length is under directional selection towards longer styles as a mechanism for mate choice among pollen of variable quality

How promising are endophytic fungi as alternative sources of plant secondary metabolites?

In this article the authors discusses the use of endophytic fungi as substitute of plant secondary metabolites. It states that endophytic fungi exist internally in plants and enhance the plants' ability to tolerate abiotic and biotic stresses. Endophytic fungi if cultured outside their host can produce secondary metabolites such as anti-cancer, anti-fungal, anti-diabetic and immunosuppressant compounds

Prospecting for alternate sources of shikimic acid, a precursor of Tamiflu, a bird-flu drug

Shikimic acid, more commonly known by its anionic form, shikimate, is an important intermediate compound of the ‘shikimate pathway’ in plants and microorganisms1. It is the principal precursor for the synthesis of aromatic amino acids,phenylalanine, tryptophan and tyrosine and other compounds such as alkaloids, phenolics and phenyl propanoids2. It is used extensively as a chiral building block for the synthesis of a number of compounds in both pharmaceutical and cosmetic industries3. In the recent past, the focus on shikimic acid has increased since it is the key precursor for the synthesis of Tamiflu, the only drug against avian flu caused by the H5N1 virus4,5. Shikimic acid is converted to a diethyl ketal intermediate, which is then reduced in two steps to an epoxide that is finally transformed to Tamiflu6

Patterns of accumulation of camptothecin, an anti-cancer alkaloid in Nothapodytes nimmoniana Graham., in the Western Ghats, India: Implications for identifying high-yielding sources of the alkaloid

Camptothecin, a monoterpene indole alkaloid, is regarded as one of the most promising anticancer drugs of the twenty-first century. Among the various plant sources, the highest yields of the alkaloid are reported from Nothapodytes nimmoniana (Icacinaceae), a small tree distributed in the Indian subcontinent. Because of the enormous demand for the chemical worldwide, there has been an indiscriminate extraction of the trees from many parts of India, especially from the Western Ghats, a mega-diversity forest range along the western coast of India. Recently the tree has been assigned a vulnerable status. In an effort to conserve the remaining populations of the species and to identify high-yielding sources of the alkaloid, attempts are being initiated in chemically profiling the species. As a first step in this direction, we have attempted to establish the general patterns of accumulation of camptothecin in N. nimmoniana across individuals, plant parts, plant size and sex of plants, in the Western Ghats. Individual trees with as high as 100 per cent greater camptothecin content than hitherto reported have been found. The study indicates the potentiality of further screening populations of N. nimmoniana to identify high-yielding sources that can be used for developing in vitro production systems or for establishing high-yielding clonal populations

Attenuation of camptothecin production and negative relation between hyphal biomass and camptothecin content in endophytic fungal strains isolated from Nothapodytes nimmoniana Grahm (Icacinaceae)

Endophytic fungi, a group of fungi living inside the host plant tissues without causing visible symptoms of disease, are known to occur ubiquitously in plants. Existing in a mutualistic association with their host plants, they have been shown to enhance the plant’s ability to tolerate abiotic and biotic stresses3. In culture, many endophytic species have been shown to produce a number of important secondary metabolites including anticancer,antidiabetic, antifungal and immunosuppressant compounds. Many of these compounds closely mimic those produced by the respective host plants, suggesting that the fungi could in fact potentially serve as an alternative source of plant secondary metabolites. Notwithstanding these findings, to date, there has been no major breakthrough in commercially exploiting the endophytic fungi as a source of important secondary metabolites. Among the reasons attributed is the severe attenuation of production of the secondary metabolite by the fungi in culture. Li et al. showed that successive cultures of an endophytic fungi Pericornia sp. isolated from Torreya grandifolia, resulted in the attenuation of taxol production, though the fungal growth itself was unaffected. Although the reasons for such attenuation are not extensively studied, it is conjectured that it could be due to lack of host stimulus in the culture media

Development of micro satellite markers for a critically endangered species, Ceropegia fantastica from the Western Ghats, India

Ceropegia fantastica L. (Asclepiadaceae) is a highly endemic and endangered species in the Western Ghats of India. Fourteen microsatellite markers were developed for C. fantastica. Eight microsatellite primers screened had 2–5 alleles per locus and the observed and expected heterozygosity ranged from 0.48 to 0.83 and 0.48 to 0.62, respectively. The primers were also evaluated for their cross amplification against two related species Ceropegia hirsuta and Ceropegia oculata. The microsatellites developed for this species could be used for addressing population genetics of this endemic and critically endangered species

Sequestration of Camptothecin, an Anticancer Alkaloid, by Chrysomelid Beetles

Camptothecin (CPT), a monoterpene indole alkaloid, is a potent inhibitor of eukaryotic toposiomerase-I. Several derivatives of CPT are in clinical use against ovarian and lung cancers. CPT has been reported from several plant species belonging to the order Asterids, with the highest concentration in Nothapodytes nimmoniana (family Icacinaceae). In this paper, we report an intriguing observation of chrysomelid beetles (Kanarella unicolor Jacobby) feeding on the leaves of N. nimmoniana without any apparent adverse effect. LC-MS/MS analysis of the beetles indicated that 54.9% of the ingested CPT’s was recovered from the wings, followed by lesser amounts in the head and abdomen. LC-HRMS analysis revealed that most of the CPT in the insect body was in the parental form available in the plants without any major metabolizable products, including sulfated and glucuronilated forms. The mechanism by which the beetles are able to tolerate substantially high levels of CPT in their body tissue is under investigation

Rattan species richness and population genetic structure of Calamus flagellum in North-Eastern Himalaya, India

Rattans, the climbing palms, are one of the most important non-wood forest produce supporting the livelihood of many forest dwelling communities in India. However, extensive harvest, loss of habitat and poor regeneration has resulted in dwindling of rattan populations necessitating an urgent need to conserve the existing rattan genetic resources. In this study, using GIS tools, an attempt has been made to develop species richness maps of rattans in the North-Eastern Himalaya, a mega-diversity region in India. At least four sites of extremely high species richness were identified that could be prioritized for in situ conservation. Further, using molecular tools, genetic variability was assessed in six populations of an economically important rattan, Calamus flagellum. The population that was least disturbed or harvested maintained comparatively higher levels of genetic diversity than those that were disturbed. The study, perhaps the first in the region, emphasizes the need for developing strategies for the long-term conservation of rattans in the North-Eastern Himalaya