Dibyendu Talukdar

Exogenous calcium alleviates the impact of cadmium-induced oxidative stress in Lens culinaris medic. Seedlings through modulation of antioxidant enzyme activities

The effect of calcium (Ca) on lentil (Lens culinaris Medic.) seedlings exposed to cadmium (Cd) stress was studied by investigating plant growth and antioxidant enzyme activities. Plants were grown for 14 days in full-strength Hoagland nutrient media supplemented with Cd concentrations of 0, 10, 20, and 40 μM, and on corresponding medium supplied with 5 mM Ca(NO3)2 prior to Cd addition. Increasing Cd led to accumulation of metal and reduced the fresh weight of the shoots more strongly than that of the roots. Cd concentrations of 20 and 40 μM were selected to study its toxic effect on seedlings. Activities of superoxide dismutase, ascorbate peroxidase, catalase, dehydroascorbate reductase, and glutathione reductase decreased at much higher magnitude in the shoots than those observed in the roots under Cd exposure. Failure of antioxidant defense in scavenging of reactive oxygen species was evidenced by abnormal rise in H2O2, resulting in enhancement of lipid peroxidation and membrane electrolyte leakage as the marks of Cd-induced oxidative stress in lentil seedlings. Ca priming in the media significantly reduced the Cd accumulation and considerably alleviated the adverse impact of Cd treatment by modulating the antioxidant enzyme activity. Mitigation of Cd-induced stress by Ca application was strongly suggested by declining levels of H2O2 and consequent lowering of oxidative damage of membrane. Consequently, this enhanced fresh mass of plant parts as the sign of Ca-mediated normal growth in Cd-treated lentil seedlings.

Meiotic consequences of selfing in grass pea (Lathyrus sativus L.) autotetraploids in the advanced generations: Cytogenetics of chromosomal rearrangement and detection of aneuploids

Meiotic consequences of an induced autotetraploid population were studied in advanced C4 and C5 selfing generations of grass pea (Lathyrus sativus L.). The tetraploids (2n = 4x = 28) segregated into progenies of normal tetraploid (NTT), tetraploid carrying reciprocal translocation (RTT), and aneuploids. Like its parent, NTT plants exhibited quadrivalent formation at meiosis I. The RTT plants, by contrast, consistently formed octavalent always in association with nucleolus at diakinesis, indicating involvement of nucleolar organizing chromosome in translocation at heterozygous condition. Both NTT and RTT plants showed higher bivalent formation than multivalent, although the latter manifested significantly better fertility and seed yield than NTT. Presumably, higher frequency of 8-shaped octavalent than ring configuration along with uniform occurrence of 10 bivalents ensured production of viable gametes in RTT plants. Among the aneuploids, pentasomy-trisomy (2n = 4x + 1 − 1 = 28) possessed a ring of nine chromosomes in RTT-derived progeny but an association of five chromosomes in NTT-selfed progeny. This suggested addition of translocated chromosome in the former case but quite normal one for the latter. However, the loss of one non-homologous chromosome in this aneuploid led the total chromosome number unaltered. Loss of one chromosome in tetrasome also led to formation of a primary trisomic (2n = 4x − 1 = 27), showing either ‘Y’ or frying pan-shaped trivalent. Two pentasomics, one single (2n = 4x + 1 = 29) and another double (2n = 4x + 1 + 1 = 30), showed formation of pentavalent/s regularly at metaphase I. The former two aneuploids showed higher fertility than pentasomics. The fitness of present autotetraploid has been discussed in the light of chromosomal rearrangement and regularization of meiotic process in grass pea.

Arsenic-induced changes in growth and antioxidant metabolism of fenugreek

The effects of arsenic (As) on growth and antioxidant metabolism of fenugreek (Trigonella foenum-graecum L. cv. Azad) plants were studied using 10, 20, and 30 mg As/kg of soil in a pot experiment under controlled conditions. The length and dry weights of shoots and roots, photosynthetic traits, and grain yield components exhibited a significant increase over control (0 mg As/kg) at As20 but decreased markedly at As30. The cause of this completely reverse response of plant growth between As20 and As30 was investigated in the backdrop of H2O2 metabolism by analyzing responses of three prominent antioxidant enzymes, namely superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT) along with cellular ascorbate pool and its redox state. Despite a significant increase in the H2O2 content in both As20 and As30 plants, the former, unlike As30 plants, did not experience any type of As-induced oxidative stress (membrane lipid peroxidation, electrolyte leakage). Normal to high levels of leaf APX, CAT, and redox pool of ascorbate effectively balanced the elevated SOD activity at As20, maintaining the H2O2 concentration higher than control but obviously in favor of As20 plant growth. By contrast, soil amendment with phosphorus (200 mg P/kg) at As30 prevented As-induced oxidative stress through the reduction of the H2O2 level even below As0. The increased enzyme activity was mainly due to the induction of unique Cu/Zn, Fe, and Mn isoforms of SOD and APX-3/APX-4 and/or their increased expression in coordination with CAT. The detection of novel isoforms suggests a strong response of H2O2-metabolizing enzymes against As-induced oxidative stress in fenugreek.

Response of antioxidative enzymes to arsenic‑induced phytotoxicity in leaves of a medicinal daisy, Wedelia chinensis Merrill

Background: Wedelia chinensis Merrill (Asteraceae) is a medicinally important herb, grown abundantly in soils contaminated with heavy metals, including toxic metalloid arsenic (As). The leaves have immense significance in treatment of various ailments. Objective: The present study was undertaken to ascertain whether the edible/usable parts experience oxidative stress in the form of membrane damage during As exposure or not. Materials and Methods: Responses of seven antioxidant enzymes were studied in leaves under 20 mg/L of As treatment in pot experiment. Results: When compared to control, activities of superoxide dismutase, monodehydroascorbatereductase, dehydroascorbatereductase, glutathione reductase, and gluathione peroxidase had increased, while the catalase level reduced and ascorbate peroxidase activity changed non-significantly in As-treated seedlings. This suggested overall positive response of antioxidant enzymes to As-induced oxidative stress. Although hydrogen peroxide content increased, level of lipid peroxidation and magnitude of membrane damage was quite normal, leading to normal growth (dry weight of shoot) of plant under Astreatment. Conclusion: W.chinensis is tolerant of As-toxicity, and thus, can be grown in As-contaminated zones.

Superoxide-Dismutase Deficient Mutants in Common Beans (Phaseolus vulgaris L.): Genetic Control, Differential Expressions of Isozymes, and Sensitivity to Arsenic

Two common bean (Phaseolus vulgaris L.) mutants, sodPv 1 and sodPv 2, exhibiting foliar superoxide dismutase (SOD) activity of only 25% and 40% of their mother control (MC) cv. VL 63 were isolated in EMS-mutagenized (0.15%, 8 h) M2 progeny. Native-PAGE analysis revealed occurrence of Mn SOD, Fe SOD, Cu/Zn SOD I and Cu/Zn SOD II isozymes in MC, while Fe SOD, and Mn SOD were not formed in sodPv 1 and sodPv 2 leaves, respectively. In-gel activity of individual isozymes differed significantly among the parents. SOD deficiency is inherited as recessive mutations, controlled by two different nonallelic loci. Gene expressions using qRT PCR confirmed higher expressions of Cu/Zn SOD transcripts in both mutants and the absence of Fe SOD in sodPv 1 and Mn SOD in sodPv 2. In 50 μM arsenic, Cu/Zn SODs genes were further upregulated but other isoforms downregulated in the two mutants, maintaining SOD activity in its control level. In an F2 double mutants of sodPv 1 × sodPv 2, no Fe SOD, and Mn SOD expressions were detectable, while both Cu/Zn SODs are down-regulated and arsenic-induced leaf necrosis appeared. In contrast to both mutants, ROS-imaging study revealed overaccumulation of both superoxides and H2O2 in leaves of double mutant.

Cytogenetics of a reciprocal translocation integrating distichous pedicel and tendril-less leaf mutations in Lathyrus sativus L.

Grass pea (Lathyrus sativus L.) is a crop with 2n = 2x = 14 chromosomes. Two variants were isolated from 250 Gy gamma ray treated M2 progenies of variety BioL-203: (i) two pedicels per peduncle (distichous pedicel); and (ii) complete absence of tendril in leaf (tendril-less). Occurrence of quadrivalents at meiosis I and partial pollen sterility (48.50%) indicated that the plants were heterozygous for a reciprocal translocation (RT), and were tentatively designated as RT-7. It transmitted at an average of 44% in the progeny, and along with normal fertile plants (N/N), produced trisomic plants (5.76%) with association of five chromosomes in selfed and intercrossed progenies. Test of independence of this newly found translocation was performed by analyzing the pattern of chromosomal ring formation at meiosis I in the F1 progeny of crosses between RT-7 and six previously detected RT lines. Presence of a ring of six chromosomes in F1 plants indicates that the two translocations have one chromosome in common in crosses between RT-7 and RT-2, RT-3, RT-5 and RT-6, but possessed two different chromosomes in RT-7 × RT-1 and in RT-7 × RT-4. The two mutant traits assorted independently in F2 and back cross progenies of N/N plants. However, a strong deviation of segregation of four phenotypes derived from N/N × RT-7 from normal F2 and back cross ratios revealed tight linkages among translocation breakpoint, distichous pedicel and tendril-less leaf. The results suggested that the two mutations, distichous pedicel and tendril-less leaf, which assorted independently in N/N plants, were integrated on a single chromosome by a reciprocal translocation in RT-7 line.

Comparative morpho-physiological and biochemical responses of lentil and grass pea genotypes under water stress

Background: Both lentil (Lens culinaris Medik.) and grass pea (Lathyrus sativus L.) in the family Fabaceae are two important cool-season food legumes, often experiencing water stress conditions during growth and maturity. Objective: The present study was undertaken to ascertain the response of these two crops under different water stress regimes. Materials and Methods: Different morpho-physiological and biochemical parameters were studied in a pot experiment under controlled environmental conditions. Along with control (proper irrigation, 0 stress), three sets of plants were subjected to mild (6 d), moderate (13 d) and severe (20 d) water stress by withholding irrigation at the appropriate time. Results: Compared with control, plant growth traits and seed yield components reduced significantly in both crops with increasing period of water stress, resulting in lowering of dry mass with more severe effect on lentil compared with grass pea. Foliar Relative Water Content (RWC) (%), K+/Na+ ratio, chlorophyll (chl) a, chl a/b ratio, stomatal conductance and net photosynthetic rate declined considerably in both crops under water stress. Leaf-free proline level increased significantly in both crops, but it decreased markedly in nodules of lentil and remained unchanged in grass pea. Nodulation was also affected due to water stress. The impairment in growth traits and physio-biochemical parameters under water stress was manifested in reduction of drought tolerance efficiency of both crops. Conclusion: Impact of water stress was more severe on lentil compared with grass pea, and modulation of growth traits signified necessity of a detailed strategy in breeding of food legumes under water stress.

Editorial: Frontiers of Sulfur Metabolism in Plant Growth, Development, and Stress Response.

Plants assimilate inorganic sulfur and metabolize it further to organic sulfur compounds essential for plant growth, development, and stress mitigation. Animals including humans in turn depend on plants and microorganisms providing these essential compounds, such as the amino acid methionine, which they cannot synthesize. Furthermore, a number of sulfur-containing metabolites provide the characteristic tastes and smells of our food, and many of them are known to have health promoting and protective properties. Thus, adequate supply of sulfur can be a critical factor affecting crop yield and production of beneficial phytochemicals. However, because of the reduction in anthropogenic emission of sulfur dioxide to the atmosphere, particularly from developed countries, sulfur deficiency has become a problem for agriculture and in many areas sulfur fertilization is required to ensure yield, quality, and health of crops. Such an impact of sulfur has triggered research into mechanisms of sulfur metabolism in plants and its regulation. Indeed great progress has been made over the last decades as summarized in several recent reviews (Takahashi et al., 2011; Sauter et al., 2013; Calderwood and Kopriva, 2014). Starting with identification of genes encoding components of sulfur metabolism, research in molecular biology and molecular genetics has brought us toward finding regulators and signals controlling the pathway (Maruyama-Nakashita et al., 2006; Gigolashvili et al., 2007; Hirai et al., 2007), and describing natural variation in diverse sulfur related traits (Kliebenstein et al., 2001; Loudet et al., 2007; Chao et al., 2014). In addition, questions related to regulation of sulfur metabolism have been on the forefront of systems biology (Maruyama-Nakashita et al., 2003; Hirai et al., 2005; Nikiforova et al., 2005) and quantitative genetics (Loudet et al., 2007). This research topic organized in Frontiers in Plant Science has been an opportunity to present our current understanding and research progress focused on a number of interesting aspects in plant sulfur metabolism. We aimed to cover broad research topics in sulfur nutrition and metabolism by compiling diverse types of articles: original research reports to exemplify new information on questions the sulfur research community is addressing, focused reviews to provide detailed updates to specific topics, and perspectives to review a progress but also to address the questions for the next decade(s) of research. This concept found indeed a great support in the sulfur research community with 34 articles contributed by scholars representing wide disciplinary areas.

Leaf Rolling and Stem Fasciation in Grass Pea (Lathyrus sativus L.) Mutant Are Mediated through Glutathione-Dependent Cellular and Metabolic Changes and Associated with a Metabolic Diversion through Cysteine during Phenotypic Reversal

A Lathyrus sativus L. mutant isolated in ethylmethane sulfonate-treated M2 progeny of mother variety BioL-212 and designated as rlfL-1 was characterized by inwardly rolled-leaf and stem and bud fasciations. The mutant exhibited karyomorphological peculiarities in both mitosis and meiosis with origin of aneuploidy. The mitosis was vigorous with high frequency of divisional cells and their quick turnover presumably steered cell proliferations. Significant transcriptional upregulations of cysteine and glutathione synthesis and concomitant stimulations of glutathione-mediated antioxidant defense helped rlfL-1 mutant to maintain balanced reactive oxygen species (ROS) metabolisms, as deduced by ROS-imaging study. Glutathione synthesis was shut down in buthionine sulfoximine- (BSO-) treated mother plant and mutant, and leaf-rolling and stems/buds fasciations in the mutant were reversed, accompanied by normalization of mitotic cell division process. Antioxidant defense was downregulated under low glutathione-redox but cysteine-desulfurations and photorespiratory glycolate oxidase transcripts were markedly overexpressed, preventing cysteine overaccumulation but resulted in excess H2O2 in BSO-treated mutant. This led to oxidative damage in proliferating cells, manifested by severe necrosis in rolled-leaf and fasciated stems. Results indicated vital role of glutathione in maintaining abnormal proliferations in plant organs, and its deficiency triggered phenotypic reversal through metabolic diversions of cysteine and concomitant cellular and metabolic modulations.

Karyotype analysis and identification of extra chromosomes in primary aneuploid stocks of grass pea (Lathyrus sativus L.) by fluorescence chromosome banding

AbstractProminent primary aneuploid stocks namely seven primary trisomics, seven primary tetrasomics, and six double trisomic types were earlier developed in grass pea (Lathyrus sativus L.), a hardy legume. Despite distinct morphological features, identity and nature of their extra chromosome(s) were elusive, hampering assignment of desirable breeding traits into specific linkage groups. The present study aims to analyze the banding pattern and to reveal the identity of extra chromosome(s) involved in these 20 aneuploid types in grass pea. Conventional orcein banding was first done using the root-tip squash technique in all aneuploids along with disomic (2n = 2x = 14) parent, and karyomorphological features were noted. Chromosomes were classified following the total length of individual chromosomes and arranged in order of decreasing sizes, keeping their centromeres in a straight line. DNA-base specific chromomycin A3 (CMA) and 4,6ʹdiamidino-2-phenylindole (DAPI) banding pattern were finally employed to c...