Cadmium-Induced Structure Change of Pigment Glands and the Reduction of the Gossypol Content in Cottonseed Kernels

The risk of cotton production on arable land contaminated with heavy metals has increased in recent years.Cotton shows stronger and more extensive resistance to heavy metals,such as cadmium(Cd)than that of other major crops.Here,a potted plant experiment was performed to study Cd-induced alterations in the cottonseed kernel gossypol content and pigment gland structure at maturity in two transgenic cotton cultivars(ZD-90 and SGK3)and an upland cotton standard genotype(TM-1).The results showed that Cd accumulation in cottonseed kernels increased with increasing Cd levels in the soil.The seed kernel Cd content in plants grown on Cd-treated soils was 10-20 times greater than the amount in the corresponding controls.There was a significant difference in Cd accumulation in cottonseed kernels at the 400 and 600μM Cd levels.Cd accumulation was higher in SGK3 and ZD-90 than in TM-1.However,the gossypol content in cottonseed kernels was lower in SGK3 and ZD-90 than in TM-1.There was a negative correlation(r=0.550)between Cd accumulation and the gossypol content in cottonseed kernels.The density of cottonseed kernel pigment glands decreased under Cd stress.This is consistent with the change in gossypol content,which decreased under Cd stress.The damage of the cultivars ZD-90 and SGK3 from Cd poisoning was relatively low under Cd stress,while TM-1 was seriously affected and exhibited Cd sensitivity.Further studies are necessary to understand the cause of the reduced gossypol content in cotton seeds under Cd stress.

Advances in Cotton Tolerance to Heavy Metal Stress and Applications to Remediate Heavy Metal-Contaminated Farmland Soil

Heavy metal-contaminated soil is one of the major environmental pollution problems of agricultural production and human health in the world.Remediation of heavy metals in soil is one of the most popular research subjects.Different remediation strategies have been reported to remove heavy metals from contaminated soil,among which phytoremediation is the most important one.Compared with other major crops,cotton shows the strongest and most widespread resistance to abiotic stresses,such as heavy metals.Although heavy metal stress adversely affects the growth and development of cotton,cotton possesses a set of sophisticated stress-resistance strategies.As the main product of cotton is nonedible fibers,which have a large biomass and strong heavy metal absorption and enrichment capacities,cotton is an ideal crop to restore heavy metal-contaminated soils and has unique advantages in terms of both ecological and economic benefits,with great application prospects.In this review,based on domestic and foreign research results in recent years,the effects of heavy metals on cotton growth and product quality were analyzed,the heavy metal absorption,accumulation,translocation and enrichment characteristics of cotton plants were summarized,and the adaptation and tolerance mechanisms of cotton to heavy metals were explored.Furthermore,the view that cotton is an effective crop to remediate heavy metal pollution in farmland soil has been proposed,and popularization and application suggestions for planting cotton to repair heavy metal pollution have been put forward to provide a reference for the comprehensive evaluation of the economic feasibility of cotton to repair heavy metal pollution in farmland soil.

MHC polymorphism and disease-resistance to Edwardsiella tarda in six turbot(Scophthalmus maximus) families

This study examined genetic variation in the major histocompatibility complex(MHC) Class II B gene in turbot(Scophthalmus maximus) by virulent bacterial pathogen challenge.One hundred fry from each of six families were infected with Edwardsiella tarda by intraperitoneal injection.Family mortality ranged from 28.0% to 83.3%.Complete exon 2 and intron 1 sequences of MHC Class II B genes were amplified from five survivor and five non-survivor individuals per family using the clone-sequence method.Thirty-seven sequences from 60 individuals revealed 37 different alleles,25 of which were unique to this study.The 25 unique alleles belonged to 16 major allele types.Nine alleles were used to examine the association between alleles and resistance/susceptibility to disease.Five alleles were present in an individual,suggesting a minimum of three loci or copies of the turbot MHC Class II B gene.The rate of non-synonymous substitution(d N) was 2.30 and 1.58 times higher than synonymous substitution(d S) in the peptide-binding regions(PBR) and non-PBR in whole families,respectively,which suggested balancing selection on exon 2 of the MHC Class II B gene in turbot.One allele,Scma-DBB1*02,was significantly more prevalent in survivor stock than in non-survivor stock(P=0.001).Therefore,this allele might be associated with resistance to bacteria.A second allele,Scma-DBB1*10,was significantly more prevalent in non-survivor stock(P=0.021),and is likely associated with susceptibility to bacteria.