Increased urbanization and industrialization have greatly contributed to the emission of higher amount of heavy metals such as cadmium,nickel,and lead into the environment.These metals are non-biodegradable and toxic,causing much effects on plants and by extension to animals and humans,which have become a major global concern.The inherent ability of plants to resist heavy metal toxicity seems to be the most sustainable and cost-effective strategy.Castor plant is widely studied due to its tolerance to the effects of heavy metal contaminated soils,owing to its large biomass content and high accumulating capacity.Castor plants to some extent can tolerate elevated levels of heavy metals through several developed mechanisms,such as activation of antioxidant enzymes,exclusion,accumulation of proline,compartmentalization,organic acid exudation,and phytochelatins.Molecular studies have identified some stress-responsive to aid the tolerance of heavy metals in castor.Stress caused by heavy metal toxicity affects seedling growth,biomass,photosynthetic pigments,protein level,and nutrient uptake of castor plant.The response of castor,however,to these stresses differs among cultivars,metal type and concentration,and time of metal applied.This review aims to summarize the physiological responses and various defense mechanisms of castor to tolerate and eradicate heavy metal toxicity and some stress-responsive genes identified at transcriptional and posttranscriptional levels that confer metal tolerance in this plant.
In order to provide a molecular basis for selecting good hybrid combinations for the identification of castor bean germplasm resources,fingerprint and genetic diversity analysis of 52 castor bean materials from 12 regions in 5 countries were constructed by using the Functinal Markers(FMs)associated with fatty acid metabolism-related genes.A total of 72 alleles were amplified by 29 pairs of FMs with an average of 2.483 per marker and the polymorphic information content was 0.103–0.695.Shannon’s information index(I),observed heterozygosity(Ho)and expected heterozygosity(He)were 0.699,0.188 and 0.436 respectively.The clustering results indicated that the castor germplasm could be divided into two groups with the genetic similarity coefficient of 0.59.The genetic similarity of 12 regions ranged from 0.518 to 0.917 and the genetic distance was between 0.087 and 0.658.A total of 5 pairs of core primers were screened to construct a digital fingerprint of different castor germplasm resources,which could distinguish all 52 germplasms.This study provides a scientific basis for screening high-quality castor germplasm resources and broadening the genetic basis of castor breeding at the molecular level.
