Heterocyclic Moieties as Prospective Nematicides: An Overview

Abstract:

Plant parasitic nematodes are destructive endoparasites having deleterious effect on about 5000 agricultural crops notably vegetables, fruits, field crops, ornamental plants, and even human health. The immense damage caused by nematodes has been estimated as US $150 billion per annum (21.3%) despite of the availability of commercialized nematicides. Nevertheless, crop protection is still dependent on the development of novel chemicals due to development of pesticide resistance line by diverse pathogens. The utilization of heterocyclic moieties in agricultural industry is considered as an effectual practice to manage plant diseases either as systemic or non-systemic. These scaffolds consist of heteroatoms in their ring structure such as N, S, O, which give a boost to their biological activity as reported. The principal heterocyclic scaffolds are the benzimidazole, pyridine, nicotinic acid, pyrrole, indole, isatin, triazine, triazole, pyrazole, amides, imidazole, cinnamic acid, oxadiazole, coumarin, thiadiazole, etc. derivatives which owing to their marvelous structural diversity are widely exploited. The prime purpose of the review is to provide information to researchers around the globe about varied heterocyclic scaffold decorations that have been employed for the synthesis of potential nematicidal candidates from 2000 onwards and their utilization to combat complex destructive biotic stress. Therefore, this review assembled the considerable synthetic chemistry and nematicidal investigation of moieties against various plant parasitic pathogens along with structure-activity relationship studies. The scientific details provided in the article will highlight the importance of heterocyclic compounds in the agricultural industry and may pave a pathway for the development of novel nematicides.

BSA-seq Identifies a Major Locus on Chromosome 6 for Root-Knot Nematode (Meloidogyne graminicola) Resistance From Oryza glaberrima

Root-knot nematode (Meloidogyne graminicola) is one of the emerging threats to rice production worldwide that causes substantial yield reductions. There is a progressive shift of the cropping system from traditional transplanting to direct-seeded water-saving rice production that favored the development of M. graminicola. Scouting and deploying new resistance genes is an economical approach to managing the root-knot nematodes. Here, we report that the inheritance of root-knot nematode resistance in Oryza glaberrima acc. IRGC102206 is governed by a single dominant gene. Traditional mapping coupled with BSA-seq is used to map nematode resistance gene(s) using the BC₁F₁ population derived from a cross of O. sativa cv. PR121 (S) and O. glaberrima acc. IRGC102206 (R). One major novel genomic region spanning a 3.0-Mb interval on chromosome 6 and two minor QTLs on chromosomes 2 and 4 are the potential genomic regions associated with rice root-knot nematode resistance. Within the QTL regions, 19 putative candidate genes contain 81 non-synonymous variants. The detected major candidate region could be fine mapped to accelerate marker-assisted breeding for root-knot nematode resistance in rice.

RACK1 inhibits colonic cell growth by regulating Src activity at cell cycle checkpoints

Previously, we showed that Src tyrosine kinases are activated early in the development of human colon cancer and are suppressed as intestinal cells differentiate. We identified RACK1 as an endogenous substrate, binding partner and inhibitor of Src. Here we show (by overexpressing RACK1, depleting Src or RACK1 and utilizing cell-permeable peptides that perturb RACK1's interaction with Src) that RACK1 regulates growth of colon cells by suppressing Src activity at G(1) and mitotic checkpoints, and consequently delaying cell cycle progression. Activated Src rescues RACK1-inhibited growth of HT-29 cells. Conversely, inhibiting Src abolishes growth promoted by RACK1 depletion in normal cells. Two potential mechanisms whereby RACK1 regulates mitotic exit are identified: suppression of Src-mediated Sam68 phosphorylation and maintenance of the cyclin-dependent kinase (CDK) 1-cyclin B complex in an active state. Our results reveal novel mechanisms of cell cycle control in G(1) and mitosis of colon cells. The significance of this work lies in the discovery of a mechanism by which the growth of colon cancer cells can be slowed, by RACK1 suppression of an oncogenic kinase at critical cell cycle checkpoints. Small molecules that mimic RACK1 function may provide a powerful new approach to the treatment of colon cancer.

Influence of W-7, a calmodulin antagonist on phospholipid biosynthesis in Candida albicans

AIM

This study was undertaken to investigate the role of calmodulin in phospholipid biosynthesis in Candida albicans using W-7, a calmodulin antagonist.

METHODS

Cells were grown as shake cultures in the absence and presence of W-7 at different concentrations. Changes in cell mass, phospholipid content and incorporation of labelled precursor into phospholipid and activities of respective enzymes have been studied.

RESULTS

Decreased incorporation of labelled acetate into total lipids and phospholipids was observed in the presence of 40 microm of W-7 which was not as a consequence of altered growth of Candida in the presence of calmodulin antagonist. Further, a significant decrease in the levels of calmodulin and CaM dependent protein kinase activity was observed in cells grown with different concentrations of W-7. This was accompanied by decreased/increased activity of phosphatidic acid phosphatase and phospholipase A, respectively in W-7 grown cells as compared to controls.

CONCLUSIONS

These findings suggest definite involvement of calmodulin in the regulation of phospholipid metabolism in Candida albicans.

Cyclin E overexpression enhances cytokine-mediated apoptosis in MCF7 breast cancer cells

Cyclin E, the regulatory component of the cyclin E/cyclin-dependent kinase (CDK) complex, is required for proliferation and overexpression of this cyclin is associated with many types of human tumors. To elucidate the mechanism by which cyclin E overexpression promotes tumorigenesis, cyclin E was overexpressed in two breast cancer lines: MCF7 and T47D. Cells overexpressing cyclin E display a marked decrease in the expression of Bcl-2, an antiapoptotic protein, and increased levels of the proapoptotic proteins Bad and Bax. The levels of Bcl-X(L) and Mcl-1 remain unchanged. Since the homeostasis of pro- and antiapoptotic proteins was altered, we asked if cyclin E overexpression modifies responses to cytokines. MCF7 cyclin E overexpressing cells have an enhanced sensitivity to Fas, TRAIL, and TNF-alpha-induced apoptosis. T47D cells overexpressing cyclin E have a significant increase in TNF-alpha and TRAIL-induced apoptosis. In conclusion, our results provide a link between expression of cyclin E, deregulation of Bcl-2, and an altered response to cytokine-mediated apoptosis.