Journal of Plant Molecular Breeding
Volume:2 Issue: 2, Summer and Autumn 2014

The plant-pathogen interaction is a multifactor process that may lead to resistance or susceptible responses of plant to pathogens. During the arms race between plant and pathogens, various biochemical, molecular and physiological events are triggered in plant cells such as ROS signaling, hormone activation and gene expression reprogramming. In plants, microRNAs (miRNAs) are key post-transcriptional regulators of gene expression and are involved in several cellular processes including response to environmental stress. In recent years, plant pathologists have presented a logical approach of plant immune system as zigzag based model that includes two phases of immunity, PTI and ETI in which miRNA molecules are determinant regulators. Here, we present an overview of miRNA biology, a brief explanation of plant immune systems in zigzag model, the role of phytohormones and miRNAs in plant immunity with a main focus on Arabidopsis-Pseudomonas interactions and finally we discuss our results on miRNA expression in lemon-Xanthomonas interactions.

Foot and Mouth Disease (FMD) is a very dangerous livestock disease which causes a serious loss in the production of milk and meat. Therefore, producing an effective recombinant subunit vaccine virus this disease is of great importance. Transient gene expression is a valuable tool to reach rapid and acceptable recombinant vaccine. An Agrobacterium-mediated transient gene expression assay was carried out in spinach (Spinacia oleracea) leaves for expression of a chimeric gene encoding a part of capsid protein of Foot and Mouth Disease virus called VP1. The plant leaves were transformed via agroinfiltration procedure. The presence of foreign gene and its expression in transformed plants were confirmed through polymerase chain reaction (PCR), real time PCR, protein Dot blot and ELISA. The results obtained in this examination showed quite a high level of gene expression in spinach leaves, showing that transient gene expression can be applied as an effective and time-saving procedure for the production of recombinant proteins. The procedures for transformation, detection of recombinant protein and its application for molecular experiments are described in the study.

Marker assisted selection (MAS) is a tool for breeding, screening, and genetic characterization of germplasm. Allelic variation of both high and low molecular weight glutenin subunits (HMW/LMW-GS) is associated with the rheological properties of wheat flour. In this study, we investigated glutenin pattern using SDS-PAGE and their PCR based on DNA markers in 60 advanced wheat lines and cultivars with different origins. Specific DNA markers regarding to Glu-1 loci, such as 1319 bp, 669 bp and 450 bp fragments were respectively validated for 2*, 17+18, 5+10 alleles. These alleles showed the highest allelic percentage in Glu-1 loci in studied cultivars. However the Null, 7+8 and 5+10 alleles showed the highest allelic percentage in advanced lines. In this study, 23%, 40% and 37% of cultivars respectively, got good (10), moderate (8-9) and weak (4-7) quality scores. In advanced lines, 18%, 44% and 38% got good, moderate and weak quality scores respectively. Ten specific DNA PCR markers were also detected for genotyping Glu-B3 alleles. The most frequent Glu-B3 alleles in wheat cultivars were i, a, b and d with 24%, 21%, 20% and 12%, respectively.Specific PCR markers regarding to the reported Glu-B3 alleles were produced as 621bp, 1095bp, 1570 bp and 662bp consequently. The most frequent Glu-B3 alleles in advanced lines belonged to a, i and d alleles with 35%, 26% and 21% respectively. The results provided useful information for breeding program to improve breadmaking quality and develop new cultivars.

Literatures have reported that a lot of drought related genes were cloned and individual gene showed positive effects under controlled stress experiments, but were not much effective in the field. Although, the progresses by conventional breeding approaches were achievable as some drought varieties have been released to the farmers in the recent years but this is not adequate to cope up with the future demand of high yield for rice, as drought seems to spread to more regions and seasons. Therefore, marker assisted selection came into lime light for accelerating and giving pace to plant breeding.From the cross (Sarjoo- 52× Nagina- 22) × Sarjoo- 52, plants were selected on the basis of presence of gene MQTL1.1responsible for the drought tolerance. These lines have been subjected to further breeding and trial tests. Agronomic performances and physiological behavior of these lines are also under track. The results showed that the variety Sarjoo 52 could be efficiently converted to a drought tolerant variety in a backcross generation followed by selfing and selection, involving a time of two to three years. Polymorphic markers for foreground and background selection were identified for the high yielding variety to develop a wider range of drought tolerant variety to meet the needs of farmers in the drought-prone regions. This approach demonstrates the effective use of marker assisted selection for a major QTL in a molecular breeding program.

DNA methylation as epigenetic mark plays a key role in normal differential and developmental processes as well as in dynamic gene regulation at the genomic level. To assess DNA methylation pattern in different developmental stages of Aeluropus littoralis, methylation sensitive amplified polymorphism (MSAP) was used. Methylation and demethylation status at the CCGG recognition site were tracked by two sets of cytosine methylation-sensitive enzymes (MspI and HpaII), which were classified into three types. The percentage of total bands per type I (non methylation), type II (CpG methylation) and type III (CpCpG methylation) fragments were 75.7, 19.4 and 4.9, respectively. The most frequent methylation events (19.4%) were observed in type II fragment in which full methylation pattern occurred. Out of 480 bands, 33 bands showed methylation alterations between differential developmental stages in all three types of detectable methylation levels. In this study, polymorphic bands had two main directions associated with methylation or demethylation patterns in which methylation level increased during plant development. The methylation and demethylation events at CG sites could be related to developmental stage-specific gene regulation.

Many agriculturally important traits are complex, affected by many genes and the environment. Quantitative trait loci (QTL) mapping is a key tool for studying the genetic structure of complex traits in plants. In the present study QTLs associated with yield and agronomical traits such as leaf number, leaf length, leaf width, plant height, stem and head diameter were identified by using 70 recombinant inbred lines (RILs) from the cross (♀) PAC2 × RHA266(♂). RILs and their parents were evaluated in a rectangular 8´9 lattice design with two replications. High genetic variability and transgressive segregation were observed in all studied traits. Genetic gain representing the difference between 10% of selected RILs and their parents was significant for most of the studied traits. Positive and significant genotypic and phenotypic correlations were observed among the studied traits. QTL analysis was performed using a recently developed SSR and SNP sunflower linkage map. The map consists of 210 SSRs and 11 SNP markers placed in 17 linkage groups (LGs). The total map length is 1,653.1 cM with a mean density of 1 marker per 7.44 cM. Composite interval mapping (CIM) procedure detected 21 QTLs involved in genetic control of studied traits. The phenotypic variance explained by the identified QTLs varied from 1.13 to 73.70%. QTLs such as HMBPP associated with the expression of more than one trait could increase the efficiency of marker-assisted selection (MAS) and genetic progress in sunflower.

There is no functional annotation for the majority of the several hundreds of receptor-like kinases in plants. A direct way of inferring the function of these proteins is to study the phenotype that results from loss of function mutants such as T-DNA mutant lines. In this research a function (phenotype) to At2g37050 gene that encodes a receptor like kinase in Arabidopsis T-DNA line was assigned. This phenotype has a shorter primary root length at later stages of development. Transcription study of the gene showed some tissue specificity with more expression level in the root in comparison with other tissues. To study genes co-expressed with At2g37050, ATTED-II web tool was used. It was found that the CLASP gene is co-expressed with At2g37050with aPearson correlation > 0.6. In kinematic analysis of the difference in root growth, the length between the root tip and the first epidermal cell with a visible root hair bulge for 8 day-old seedlings of wild type plants was 1327± 76.50 µm (n=6) and for the mutant plants, was 1109± 72.28. This parameter of the wild type and the mutant plants shows that loose of function of At2g37050 gene, reduce cell elongation in the elongation zone of root.