Alvina Gul Kazi

Alleviation of cadmium toxicity in Brassica juncea L. (Czern. & Coss.) by calcium application involves various physiological and biochemical strategies.

Calcium (Ca) plays important role in plant development and response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effect of Ca (50 mM) in controlling cadmium (Cd) uptake in mustard (Brassica juncea L.) plants exposed to toxic levels of Cd (200 mg L−1 and 300 mg L−1). The Cd treatment showed substantial decrease in plant height, root length, dry weight, pigments and protein content. Application of Ca improved the growth and biomass yield of the Cd-stressed mustard seedlings. More importantly, the oil content of mustard seeds of Cd-stressed plants was also enhanced with Ca treatment. Proline was significantly increased in mustard plants under Cd stress, and exogenously sprayed Ca was found to have a positive impact on proline content in Cd-stressed plants. Different concentrations of Cd increased lipid peroxidation but the application of Ca minimized it to appreciable level in Cd-treated plants. Excessive Cd treatment enhanced the activities of antioxidant enzymes superoxide dismutase, ascorbate peroxidase and glutathione reductase, which were further enhanced by the addition of Ca. Additionally, Cd stress caused reduced uptake of essential elements and increased Cd accumulation in roots and shoots. However, application of Ca enhanced the concentration of essential elements and decreased Cd accumulation in Cd-stressed plants. Our results indicated that application of Ca enables mustard plant to withstand the deleterious effect of Cd, resulting in improved growth and seed quality of mustard plants.

Phytoremediation of Soils: Prospects and Challenges

Abstract Contamination of the environment (i.e. soil and water) by toxic metals has become of paramount interest worldwide, owing to increasing industrialized and municipal waste affecting large areas of agricultural land. The problem of land pollution in areas such as China, America and Western Europe has led to one-sixth of the world’s total arable land being unsuitable for farming. In recent years, phytoremediation has acquired great popularity as a leading technology for the management of soil pollution. Phytoremediation refers to the use of plants to mitigate concentrations of both organic and non-organic pollutants in soil. More than 400 plant species worldwide have been identified that have the ability to extract heavy metals from the soil. This technology is more cost-effective, environmentally friendly and aesthetically pleasing than former physical approaches such as excavation, leaching using acids and reverse osmosis. Phytoremediation technology has been split into several categories, chief among which are phytoextraction, phytofiltration, phytodegradation and phytostabilization. This chapter focuses on how different plant species with hyperaccumulating abilities have been put to use extracting large concentrations of arsenic, cadmium, copper, mercury, lead and zinc from various soil types in many countries. However, certain limitations attributed to this technology, such as time consumption, season dependency and less efficient plant morphological features, have raised serious concerns regarding its widespread use. To overcome these obstacles, the use of plant biotechnology to develop new crop species with enhanced metal-extracting capabilities via mutagenesis, protoplast fusion and breeding techniques, has been the new centre of focus for plant geneticists.Contamination of the environment (i.e. soil and water) by toxic metals has become of paramount interest worldwide, owing to increasing industrialized and municipal waste affecting large areas of agricultural land. The problem of land pollution in areas such as China, America and Western Europe has led to one-sixth of the world’s total arable land being unsuitable for farming. In recent years, phytoremediation has acquired great popularity as a leading technology for the management of soil pollution. Phytoremediation refers to the use of plants to mitigate concentrations of both organic and non-organic pollutants in soil. More than 400 plant species worldwide have been identified that have the ability to extract heavy metals from the soil. This technology is more cost-effective, environmentally friendly and aesthetically pleasing than former physical approaches such as excavation, leaching using acids and reverse osmosis. Phytoremediation technology has been split into several categories, chief among which are phytoextraction, phytofiltration, phytodegradation and phytostabilization. This chapter focuses on how different plant species with hyperaccumulating abilities have been put to use extracting large concentrations of arsenic, cadmium, copper, mercury, lead and zinc from various soil types in many countries. However, certain limitations attributed to this technology, such as time consumption, season dependency and less efficient plant morphological features, have raised serious concerns regarding its widespread use. To overcome these obstacles, the use of plant biotechnology to develop new crop species with enhanced metal-extracting capabilities via mutagenesis, protoplast fusion and breeding techniques, has been the new centre of focus for plant geneticists.

High-molecular-weight (HMW) glutenin subunit composition of the Elite-II synthetic hexaploid wheat subset ( Triticum turgidum × Aegilops tauschii ; 2 n = 6 x = 42; AABBDD)

Characterization of high-molecular-weight (HMW) glutenins is an important criterion for identifying genotypes with good bread-making quality. In synthetic hexaploids (SHs), the D-genome encodes several allelic variants of HMW glutenins that require proper identification prior to their utilization for bread wheat (BW) improvement. In this study, SHs with promising agronomic features were characterized for HMW glutenin composition. Seven different allelic variants were observed at the Glu-D t 1 locus, three of which (1Dx1.5 þ 1Dy10, 1Dx1.5 þ 1Dy12.2 and 1Dx2.1 þ 1Dy10) have not been previously reported in existing BW germplasm. The results also showed a variety of D-genome-encoded subunits along with superior glutenin alleles in the B-genome (1Bx7 þ 1By8, 1Bx6 þ 1By8 and 1Bx13 þ 1By16). About 63% of these SHs encoded favourable allelic variants of HMW glutenins, which make them a good choice for improvement in wheat bread making. Glu-D t 1 encoded favourable allelic variants (1Dx5 þ 1Dy10 and 1Dx1.5 þ 1Dy10) that are frequently observed in SHs can be easily incorporated into BW through recombination breeding.

Plant secretomics: Identification, isolation, and biological significance under environmental stress

Plant secretomes are the proteins secreted by the plant cells and are involved in the maintenance of cell wall structure, relationship between host and pathogen, communication between different cells in the plant, etc. Amalgamation of methodologies like bioinformatics, biochemical, and proteomics are used to separate, classify, and outline secretomes by means of harmonizing in planta systems and in vitro suspension cultured cell system (SSCs). We summed up and explained the meaning of secretome, methods used for the identification and isolation of secreted proteins from extracellular space and methods for the assessment of purity of secretome proteins in this review. Two D PAGE method and HPLC based methods for the analysis together with different bioinformatics tools used for the prediction of secretome proteins are also discussed. Biological significance of secretome proteins under different environmental stresses, i.e., salt stress, drought stress, oxidative stress, etc., defense responses and plant interactions with environment are also explained in detail.

Heavy Metal Uptake and Transport in Plants

Like all other organisms, plants have developed different strategies to get adapted to their external environments. An increase in the metal ion concentration in soils, metallothioneins, stress proteins, etc. results into reactive oxygen species production that ultimately leads to programmed cell death. To deal with such stress situations, plants have developed certain defense mechanisms or adaptation strategies including restriction of metal ion uptake, metal export from the plant, chelation and compartmentalization, etc.; processes in which different metal transporters are involved. These transporters act through a series of signaling events which ultimately lead to the balance of nutrients in the plants, necessary for their survival. Based on the current plant molecular and biochemical research, the role of copper transporter family, ZIP family, NRAMP family of transporters, MATE protein transporters, HMA transporters, oligopeptide transporters, ABC family of transporters, and cation-diffusion facilitator family of transporters will be discussed in this chapter.

Plant exomics: Concepts, applications and methodologies in crop improvement

Molecular breeding has a crucial role in improvement of crops. Conventional breeding techniques have failed to ameliorate food production. Next generation sequencing has established new concepts of molecular breeding. Exome sequencing has proven to be a significant tool for assessing natural evolution in plants, studying host pathogen interactions and betterment of crop production as exons assist in interpretation of allelic variation with respect to their phenotype. This review covers the platforms for exome sequencing, next generation sequencing technologies that have revolutionized exome sequencing and led toward development of third generation sequencing. Also discussed in this review are the uses of these sequencing technologies to improve wheat, rice and cotton yield and how these technologies are used in exploring the biodiversity of crops, providing better understanding of plant-host pathogen interaction and assessing the process of natural evolution in crops and it also covers how exome sequencing identifies the gene pool involved in symbiotic and other co-existential systems. Furthermore, we conclude how integration of other methodologies including whole genome sequencing, proteomics, transcriptomics and metabolomics with plant exomics covers the areas which are left untouched with exomics alone and in the end how these integration will transform the future of crops.

Allelic variation and composition of HMW-GS in advanced lines derived from d-genome synthetic hexaploid / bread wheat ( Triticum aestivum L.)

The objective of this study was to identify allelic variations at Glu-1 loci of wheat (Triticum aestivum L.) advanced lines derived from hybridization of bread wheat and synthetic hexaploid wheats (2n = 6x = 42; AABBDD). Locally adapted wheat genotypes were crossed with synthetic hexaploid wheats. From the 134 different cross combinations made, 202 F8 advanced lines were selected and their HMW-GS composition was studied using SDS-PAGE. In total, 24 allelic variants and 68 HMW-GS combinations were observed at Glu-A1, Glu-B1, and Glu-D1 loci. In bread wheat, the Glu-D1 locus is usually characterized by subunits 1Dx2+1Dy12 and 1Dx5+1Dy10 with the latter having a stronger effect on bread-making quality. The subunit 1Dx5+1Dy10 was predominantly observed in these advanced lines. The inferior subunit 1Dx2+1Dy12, predominant in adapted wheat germplasm showed a comparative low frequency in the derived advanced breeding lines. Its successful replacement is due to the other better allelic variants at the Glu-D1 locus inherited in these synthetic hexaploid wheats from Aegilops tauschii (2n = 2x = 14; DD).

Phytoextraction: The Use of Plants to Remove Heavy Metals from Soil

Abstract The continuous increase in industrial activities has contaminated the soil with heavy metals such as cadmium, chromium, copper, mercury, lead, arsenic, nickel, and zinc and are nondegradable and hazardous to life. Many physiochemical methods have been proposed to remove metals from soil, but no method is completely safe and satisfactory. Phytoextraction or phytoaccumulation has emerged as a promising technique for soil remediation that can readily absorb heavy metals and purify the soil of its contaminants. Plants have a natural mechanism to take up and store nutrients according to their bioavailability in soil and the plant’s requirement. Among them, hyperaccumulators have the tendency to take up even nonessential elements by 100-fold greater than nonhyperaccumulators. Because of their larger biomass, they can gather heavy metals using ion channels and metal transport proteins through roots and store them in the above-ground organs where they are either stored in vacuoles and cell walls or detoxified. More than 450–500 plant species have been identified as hyperaccumulators including Thalaspi and Arabidopsis and members from families such as Brassicaceae , Cyperaceae , Poaceae , Fabaceae , and several others. For the plants to effectively take up heavy metal contaminants, the contaminants need to be converted into water-soluble compounds. This technique is called induced phytoextraction in which chelating agents are added in soil that desorb the toxic metals and allow easy uptake by roots. Most common chelates are ethylene diamine tetra acetate, ethylene diamine disuccinate , and other organic acids. However, they can increase toxicity of ground water and affect soil microfauna; therefore, environmental-friendly chelates need to be developed. Another strategy to detoxify soils is to create transgenic plants with increased hyperaccumulation activity against a particular metal. Hence, phytoextraction can be a perfect technique for soil purification because of its minimal limitation. This chapter will focus on the phytoextraction mechanism, metal uptake, and accumulation techniques in plants. Further, the impact of phytoextraction on environmental health will also be explained.

Comparative Assessment of Synthetic-derived and Conventional Bread Wheat Advanced Lines Under Osmotic Stress and Implications for Molecular Analysis

Drought is one of the most important environmental factors limiting wheat yield in many parts of the world. Progress in breeding to improve drought tolerance has been limited by its high sensitivity to environmental factors, low heritability, and the complexity and size of wheat genome. Two genetically diverse sets of wheat genotypes were evaluated to identify genetic resources maintaining physiological and metabolic stability under osmotic stress. Data on 13 different morphological and physiological traits under control and osmotic stress clearly depicted the superiority of wheat lines derived from synthetic hexaploid wheats (SHWs) as compared to conventional bread wheats. Accordingly, all lines were genotyped with simple sequence repeat (SSR) markers to assess the diversity and identify the marker–trait associations (MTAs). Structure analysis partitioned the germplasm into two sub-populations (K = 2) based on ΔK and LnP(D) values. Association mapping was performed using Q + K matrix as covariates by applying mixed linear model (MLM). In total, 39 MTAs over 20 SSR loci were detected by the strict MLM model, which were reduced to 12 MTAs over 6 SSR loci after strict Bonferroni adjustments. MTAs detected under osmotic stress conditions indicated the effectiveness of association mapping to identify loci for different attributes under low-moisture conditions. Conclusively, this study has demonstrated that synthetic-derived wheats harbor valuable alleles that can enrich the genetic base of cultivated wheat and improve its adaptation under water stress conditions. The MTAs detected may have the candidate genes responsible for drought adaptation, thus providing a unique resource which can be manipulated for developing drought-tolerant cultivars.

Erratum to: Heavy Metal Built-Up in Agricultural Soils of Pakistan: Sources, Ecological Consequences, and Possible Remediation Measures

Pakistan is an agricultural country with two thirds of the population depending on the agriculture sector for their livelihood. The increasing population growth rate (1.49 %) has placed an immense pressure on resources and continuous food/fiber demands from varying agroecological zones of the country. Increased agricultural production has compromised soil ecosystems in specific and agricultural environments in general. Farmers have adopted all means, i.e., agricultural mechanization, usage of pesticides, increased fertilizer use, wastewater irrigation, application of municipal and industrial solid wastes/sludges/composts, and monoculture to increase agricultural production. In response to all such anthropogenic activities, soil fertility and health are continuously on decline. Soils act as sink to all anthropogenic activities and substances either organic or inorganic, i.e., heavy metals. Ways and means employed to enhance agricultural productivity continuously add heavy metals into soil ecosystems which are extremely cytotoxic, teratogenic, carcinogenic, and mutagenic. Atmospheric deposition and vehicular emissions are also adding heavy metals to the agricultural soils. Food chain contamination is the ultimate result of increased metal levels in soils which are biomagnified in the food crops and fodder. Heavy metal contamination of food crops leads to serious health concerns in the consumers, i.e., humans and livestock. Various researchers have highlighted elevated metal levels in the agricultural soils from different agroecologies of Pakistan presenting the current status, biomagnification, and related potential ecological health problems. Chemometric and GIS approaches in this regard have been successfully employed to understand the origin, relationship, and spatial distribution patterns of heavy metals in the contaminated agricultural soils. In current review of heavy metal contamination in agricultural soils, several remediation techniques, i.e., mycoremediation, phytoremediation, and bacterial bioremediation, have also been reported from Pakistan to offer an economic, environment-friendly, and viable solution to reclaim contaminated soils. All three bioremediation types employed by different researchers in Pakistan befit the country’s energy and climatic conditions. Through genetic engineering abilities of plants, fungi and bacteria can be enhanced to attain the desired bioremediation results in polluted environments either in situ or ex situ. Good agricultural practices and reduced chemical input can slow down further heavy metal built-up in soils.