Sequence similarity based identification of abiotic stress responsive genes in chickpea

Chickpea (Cicer arietinum L.) is an important food legume crop, particularly for the arid regions including Indian subcontinent. Considering the detrimental effect of drought, temperature and salt stress on crop yield, efforts have been initiated in the direction of developing improved varieties and designing alternate strategies to sustain chickpea production in adverse environmental conditions. Identification of genes that confer abiotic stress tolerance in plants remains a challenge in contemporary plant breeding. The present study focused on the identification of abiotic stress responsive genes in chickpea based on sequence similarity approach exploiting known abiotic stress responsive genes from model crops or other plant species. Ten abiotic stress responsive genes identified in other plants were partially amplified from eight chickpea genotypes and their presence in chickpea was confirmed after sequencing the PCR products. These genes have been functionally validated and reported to play significant role in stress response in model plants like Arabidopsis, rice and other legume crops. Chickpea EST sequences available at NCBI EST database were used for the identification of abiotic stress responsive genes. A total of 8,536 unique coding long sequences were used for identification of chickpea homologues of these abiotic stress responsive genes by sequence similarity search (BLASTN and BLASTX). These genes can be further explored towards achieving the goal of developing superior chickpea varieties providing improved yields under stress conditions using modern molecular breeding approaches.     

Morphological and pathogenic variability of Indian isolates of Fusarium oxysporum f. sp. ciceris causing chickpea wilt

Wilt of chickpea (Cicer arietinum) caused by Fusarium oxysporum f. sp. ciceris is prevalent in almost all chickpea growing areas of the world and its incidence varied from 14.1 to 32.0% in the different states of India surveyed. The isolates were highly variable in their colony growth pattern, size of colony and pigmentations. The size of microconidia varied from 5.1–12.8 × 2.5–5.0 μm, whereas macroconidia ranged from 16.5–37.9 × 4.0–5.9 μm with 1–5 septations. One hundred and twelve isolates were grouped into 12 categories on the basis of their radial growth, size of macroconidia and growth pattern. Majority of the isolates were highly pathogenic causing more than 50% wilt in chickpea cultivar JG 62. Virulence analysis of 56 representative isolates on a set of 18 cultivars of chickpea, including 10 international differentials, grouped them into three categories. Chickpea cultivar KWR 108 differentiated all isolates of Punjab, Haryana and Delhi states and a few isolates of Rajasthan from others by showing resistant reactions and were placed in the first group. The rest of the isolates of Rajasthan state showed susceptible reactions on KWR 108 placed in a second group. Cultivar CPS 1 distinguished the isolates of Jharkhand state and placed them into a third group. An international set of cultivars recommended for race differentiation were not able to distinguish all the isolates into known races of the pathogen, therefore cultivar KWR 108 should be included in the existing differential set of cultivars.     

Agrobacterium-mediated transformation of chickpea with α-amylase inhibitor gene for insect resistance

Chickpea is the world’s third most important pulse crop and India produces 75% of the world’s supply. Chickpea seeds are attacked byCallosobruchus maculatus andC. chinensis which cause extensive damage. The α-amylase inhibitor gene isolated fromPhaseolus vulgaris seeds was introduced into chickpea cultivar K850 throughAgrobacterium- mediated transformation. A total of 288 kanamycin resistant plants were regenerated. Only 0.3% of these were true transformants. Polymerase chain reaction (PCR) analysis and Southern hybridization confirmed the presence of 4.9 kb α-amylase inhibitor gene in the transformed plants. Western blot confirmed the presence of α-amylase inhibitor protein. The results of bioassay study revealed a significant reduction in the survival rate of bruchid weevilC. maculatus reared on transgenic chickpea seeds. All the transgenic plants exhibited a segregation ratio of 3:1.     

Low-Temperature Stress: Implications for Chickpea (Cicer arietinum L.) Improvement

Chickpea is the third major cool season grain legume crop in the world after dry bean and field pea. Chilling and freezing range temperatures in many of its production regions adversely affect chickpea production. This review provides a comprehensive account of the current information regarding the tolerance of chickpea to freezing and chilling range temperatures. The effect of freezing and chilling at the major phenological stages of chickpea growth are discussed, and its ability for acclimation and winter hardiness is reviewed. Response mechanisms to chilling and freezing are considered at the molecular, cellular, whole plant, and canopy levels. The genetics of tolerance to freezing in chickpea are outlined. Sources of resistance to both freezing and chilling from within the cultivated and wild Cicer genepools are compared and novel breeding technologies for the improvement of tolerance in chickpea are suggested. We also suggest future research be directed toward understanding the mechanisms involved in cold tolerance of chickpea at the physiological, biochemical, and molecular level. Further screening of both the cultivated and wild Cicer species is required in order to identify superior sources of tolerance, especially to chilling at the reproductive stages.     

植物WRKY转录因子在应对盐胁迫中的作用研究进展

土壤中的高含盐量严重限制了植物的生长和作物的产量。植物的许多转录因子在植物逆境胁迫中发挥着重要的作用,但仍有很多转录因子的分子机制目前尚不清楚。WRKY转录因子作为高等植物中最大的转录因子家族之一,参与并影响着植物生长发育的多个方面,在盐胁迫的多种不同响应途径中发挥重要作用。WRKY蛋白对基因表达的调控主要是通过与DNA特定顺式调控元件——W-box元件（TTGACC）的结合来实现的。近年来,从模式植物拟南芥（Arabidopsis）到农作物,已经有许多研究揭示了WRKY家族成员的作用和机制。本文综述了WRKY转录因子在应对盐胁迫方面的最新研究进展,探讨了WRKY转录因子研究目前存在的问题和未来的展望。     

Antagonistic potential of certain legumes to Meloidgyne incognita on sugar beet

Under greenhouse conditions, a pot experiment was conducted to clarify the potential of using some legumes as intercropped plants for reducing the root-knot nematode Meloidogyne incognita infecting sugar beet (Beta vulgaris L.) cv. DS-9004 compared to non-legume plant, garlic and non-intercropped plants. The obtained results revealed that all legumes including chickpea, Egyptian clover, faba bean, fenugreek, lentil and lupin significantly (p ≤ 0.05) reduced nematode criteria on the roots of sugar beet at different degrees. Chickpea and Egyptian clover reduced the number of galls on the roots of sugar beet as the percentage of reductions were 54 and 50%, respectively, followed by lupin and fenugreek, while garlic achieved 72% reduction compared to non-intercropped plants. Lupin reduced the number of egg masses by 59% followed by Egyptian clover and fenugreek (32%), three months after the treatment. On the other hand, six months after the treatment, chickpea reduced the number of galls by 55.7% followed by lupin (53.4%) and Egyptian clover (52.3%) and the percentage of reduction of egg masses behaved the same trend. Also, the treatments improved plant growth criteria of sugar beet, weight of roots (tubers) and the percentage of total soluble solids (TSS).     

The affinity of DNA sequences containing R5Y5 motif and TA repeats with 10.5-bp periodicity to histone octamer in vitro

Nucleosome positioning along the genome is partially determined by the intrinsic DNA sequence preferences on histone. RRRRRYYYYY (R5Y5, R?=?Purine and Y?=?Pyrimidine) motif in nucleosome DNA, which was presented based on several theoretical models by Trifonov et al., might be a facilitating sequence pattern for nucleosome assembly. However, there is not a high conformity experimental evidence to support the concept that R5Y5 motif is a key element for the determination of nucleosome positioning. In this work, the ability of the canonical, H2A.Z- and H3.3-containing octamers to assemble nucleosome on DNA templates containing R5Y5 motif and TA repeats within 10.5-bp periodicity was investigated by using salt-dialysis method in vitro. The results showed that the10.5-bp periodical distributions of both R5Y5 motif and TA repeats along DNA templates can significantly promote canonical nucleosome assembly and may be key sequence factors for canonical nucleosome assembly. Compared with TA repeats within 10.5-bp periodicity, R5Y5 motif in DNA templates did not elevate H2A.Z- and H3.3-containing nucleosome formation efficiency in vitro. This result indicates that R5Y5 motif probably isn’t a pivotal factor to regulate nucleosome assembly on histone variants. It is speculated that the regulatory mechanism of nucleosome assembly is different between canonical and variant histone. These conclusions can provide a deeper insight on the mechanism of nucleosome positioning.

Communicated by Ramaswamy H. Sarma