Plant Gene最新文献

Three-line hybrid rice system is the most successful and widely practiced method around the world. Hybrid rice breeders have used B × B, A × R and R × R (R = Restorer line, B = Maintainer line, A = CMS line) scheme of parental line improvement frequently and avoided B × R and R × B scheme. As a result, female parents lack the genetic diversity carried by R lines. But B × R and R × B mating have great potential to produce high value parental lines of hybrid rice and overcome the limitation of the previous approach. We have demonstrated a new method for three-line hybrid system to minimize the barrier of crossing in parent selection for developing new elite maintainers and restorers. Parental combinations were selected based on breeding value of the genotypes. Breeding values were estimated based on ancestor, pedigree information and yield data of 74 test genotype to select parents for restorer and maintainer line improvement. This new protocol allows (B × R), (R × B) (R × Elite) and (B × Elite) improvement technique to bring out high yielding diverse B and R lines. This B line will be used for developing new A line in the genetic background of B line. Doubled haploid and RGA i.e. rapid generation advance tools of breeding will save the precious time and reduce breeding cycle length; and large population size will increase selection accuracy. We have predicted the genetic gain in parental line development for four parental cross using the studied 74 genotypes for doubled haploid and rapid generation advance methods. Our objectives were to demonstrate the new breeding approach plus breeding value and positive dominant gene effect-based parent selection strategy. We are hopeful about the new method that hybrid rice breeders across the world will extract benefit utilizing the new methodology of hybrid rice parental line development.

Erysiphe pisi is one among the other causal agents of powdery mildew infection in garden pea. So far, the resistance genes comprising two recessive (er1 and er2) and one dominant (Er3) have been reported to confer resistance to powdery mildew in garden pea. A set of 46 pea genotypes were screened against the E. pisi isolate- Ep01 in greenhouse conditions to identify resistant genotypes. Disease reaction and genotyping were carried out to test for resistance/ susceptibility through gene-specific sequence characterized amplified region (SCAR) markers. The presence of the resistance alleles in the control pea genotypes- JI2302 for er1 gene, JI2480 for er2 gene and P660–4 for Er3 was confirmed through their respective gene-specific markers. The pea genotype- Arkel served as a negative control. Screening of the pea germplasm revealed 3 genotypes as highly resistant, 6 genotypes as resistant while 10 genotypes were moderately resistant, 13 genotypes were moderately susceptible, 9 genotypes were susceptible and 5 were highly susceptible. The molecular marker for er1 resistance gene Sc-OPE-16₁₆₀₀ was found to be segregating in most of the pea genotypes except in the susceptible control- Arkel. The marker- ScX17_1400 for er2 gene was found to be in homozygous condition in the resistant pea genotypes while the marker associated with Er3 resistance, SCW4₆₃₇, was found to be in heterozygous condition in majority of the pea genotypes except in the resistant control genotype- P660–4.

Origin and evolution of secondary cell wall is considered key to colonization of terrestrial habitat by plants. The primary component of secondary cell wall, lignin, imparts strength and rigidity and enables plants to endure negative pressure created during transpiration. Members of the MYB transcription family, AtMYB42 and AtMYB85, play critical roles as regulators of lignin biosynthesis. Inspite of their functional significance, evolutionary history of homologs of AtMYB42 and AtMYB85 across land plants remains to be investigated. Our analysis revealed that homologs of AtMYB42 and AtMYB85 as two distinct genes are not present in any plant lineage outside Brassicaceae and only the ancestral form exists as AtMYB42/AtMYB85. Analysis of homologs of AtMYB42 and AtMYB85 across green plants combined with comparative genomics, selection pressure, and character-state reconstruction reveals that AtMYB42 and AtMYB85 are paralogous, and arose via segmental duplication, which may coincide with the α-event of WGD that occurred after the split of Brassicaceae-Caricaceae from the last common ancestor. Within Brassicaceae, homeologs and paralogs that arose as a result of polyploidization, and species- and lineage-specific changes could be observed. For instance, homologs of AtMYB42 were found to be deleted from the entire Brassica lineage. Analysis of homeologous segments in neopolyploids (B. napus, B. juncea, Camelina sativa), and meso-polyploid (B. rapa) revealed differential degrees of gene loss and retention. In Brassicaceae, homologs of AtMYB42 were found to be under purifying selection and of AtMYB85 under positive selection. High sequence identity in the coding region between homologs of AtMYB42 and AtMYB85 is indicative of redundant roles, and the loss of homologs of AtMYB42 in Brassica may be compensated by presence of AtMYB85 homologs and homeologs. The study thus forms the basis to investigate questions on regulatory diversification owing to variation in cis-elements between the paralogs and among homeologs, and, impact of differential selection pressure vis-a-vis redundant function.

Insect and pathogen damage of maize inhibits sustainable production. Discovery of maize genes coding for products active against both classes of pests would significantly accelerate the rate of development of resistant varieties. A quinone oxidoreductase gene homologous to apoptosis related P53 inducible gene 3 (PIG3) in vertebrates was identified as a pest resistance candidate in a quantitative trait locus region for maize ear rot resistance. The quinone oxidoreductase gene was cloned from a Fusarium resistant inbred of maize and expressed in maize callus. The transformed callus had some significant resistance to the maize pathogen F. graminearum, compared to control transformants, and was often highly resistant to two major caterpillar pests of maize. A band of enhanced reactive oxygen species (ROS) generation in the presence of relevant substrates was noted when protein extracts from the transgenic callus compared to those from control callus were separated by polyacrylamide gel electrophoresis. Thus, presence or introduction of an optimally functional form of this gene should lead to enhanced resistance of maize and other crops to major insect and fungal pests.

MicroRNAs (miRNAs) are a class of small non-coding RNAs that act as important modulators of gene expression related to several stress responses in plants. While several miRNAs have been implicated in the modulation of multiple abiotic and biotic stresses in rice, there role in response to fluoride stress is yet to be explored. In the present study, fourteen conserved rice miRNAs with proven role in multiple stress response were analysed to identify differentially expressed miRNAs in response to fluoride toxicity in two popular rice varieties- Gobindobhog (GB; F-tolerant) and IR64 (F-sensitive). Stem-Loop RT-PCR revealed that miR156, miR166, and miR171 were significantly induced in GB seedlings post treatment with fluoride. Likewise, miR160, miR319, miR396, and miR444 were prominently induced in the fluoride-sensitive IR64. Additionally, miR393 was significantly induced post-treatment with fluoride stress in both the genotypes exhibiting a basal response to fluoride toxicity. Further, we computationally predicted the miRNA targets many of which encoded transcription factors associated with stress response mechanism. The miRNA targets were experimentally validated using ligation mediated 5′ rapid amplification of cDNA ends analysis. Quantitative RT-PCR analysis of nine selected miRNA target genes (Os11g30370, Os06g47150, Os06g03670, Os04g48290, Os02g44360, Os08g34380, Os05g05800, Os04g57050, Os04g51350) revealed simultaneous reciprocal changes in the expression patterns of the miRNAs and the corresponding target genes suggesting their involvement in the modulation of fluoride stress response in rice. Analysis of proximal promoter sequences of the F-responsive miRNAs revealed that these miRNAs possess stress-responsive, elicitor and hormonal related motifs. Overall, our results suggest that multiple conserved miRNAs are involved in fluoride toxicity and a miRNA-mediated regulation of signal response is critical for rice response to fluoride stress.

Melanoxylon brauna is a tree species native to the Atlantic Forest that has great potential for reforestation and urban afforestation. Due to its exploitation, germination difficulties, and absence in afforestation projects, it is currently endangered. Therefore, this study aims to evaluate the diversity and genetic structure in M. brauna matrixes established in multiclonal minigardens through inter simple sequence repeat (ISSR) markers. Plant material of 59 individuals arranged in the multiclonal minigarden was collected for the analyses. Eleven ISSR primers were selected, which generated 183 fragments, among which 117 were polymorphic (63,93%). The efficiency of the markers was confirmed through the polymorphism information content (PIC) which resulted in an average value of 0.36, characterizing them as moderately informative. High genetic diversity was found based on the values of the number of observed alleles (A_O = 2.00) and effective alleles (A_E = 1.63), Nei's diversity index (H* = 0.36), Shannon index (I* = 0.54), and the formation of distinct groups by cluster analysis. Despite the alleles being well distributed among individuals, revealing high genetic diversity, Bayesian inference revealed only one genetic group (K = 1). The ISSR markers proved to be efficient in the characterization of the genetic diversity in M. brauna individuals, and the population of the multiclonal minigarden can be used as a source of propagules for seedling production. However, actions such as the expansion of the genetic diversity through the introduction of plants from different origins can increase the adaptive potential of the minigarden and future established populations.

Salinity is a stress factor that decreases global agricultural yield. Crops such as rice, tomato, potato, and legumes are susceptible to salt, thus this problem requires urgent attention. Disruption of carbohydrate metabolism can have negative effects on stress tolerance. Sucrose phosphate synthase (SPS) enzymes operate in a key regulatory step in sucrose synthesis. Therefore, they have a significant role in the regulation of sugar metabolism. This study focused on the function of the SPS homolog -pvSPS4- in the roots of legume crop common bean under salinity stress. We previously showed that pvSPS4 expression is root-specific and is upregulated under salt stress in a salt-tolerant common bean genotype. This upregulation was accompanied by an accumulation of sugars in the roots. In the current study, using the same genotype, we generated composite common bean plants with wild-type shoot and pvSPS4 knock-down roots. Composite plants exhibited a more sensitive phenotype under salt stress compared to control and mock plants. pvSPS4 knock-down disturbed the root glucose/sucrose ratio and balance of Ca⁺², Mg⁺², and K⁺ in both root and leaves which resulted in a reduction in photosynthetic pigments together with osmoregulation and antioxidant capability. Our results imply that pvSPS4 is an important gene for carbohydrate balance regulation under salt-stress in the common bean root tissues and sets an example for the significance of mainly disregarded roles of SPS genes in sink tissues.

Eucalyptus is one of the mainstays of the forest industry, contributing high-quality raw materials for pulp, paper, wood, and energy production. The typical approaches to reveal the genetic basis of important traits include classical Quantitative Trait Locus (QTL) mapping and Genome-Wide Association Studies (GWAS) approaches, but these are typically expensive and time-consuming. Here we evaluate the potential of Extreme-Phenotype GWAS (XP-GWAS) to identify candidate genes underlying a quantitative trait in Eucalyptus, using the timing of leaf heteroblasty as a case study. XP-GWAS involves genotyping pools of individuals grouped by extreme and opposed phenotypes from a population or a diversity panel and studying their allele frequency. Using a previous phenotyped trial of E. globulus, we sequenced pools of 50 individuals that notably differ in the onset of adult foliage. Since the genetic basis of heteroblasty is well understood, we first searched for previously identified genes. Secondly, we searched for new candidate genes and also evaluated the copy number variation (CNVs) that may be involved in this process. We found marginally significant SNPs associated with previously described microRNAs, and interesting new non-coding RNAs. Disease resistance genes were also uncovered, probably as a consequence of indirectly selecting resistant trees, although a possible interaction between resistance and heteroblasty cannot be disregarded either. Our work shows the utility and limitations of XP-GWAS analysis to explore the genetic basis of Eucalyptus.

Molecular markers play an effective role in estimating the genetic similarity, variation, diversity, and population structure of different plants. Various factors associated with in vitro culture conditions may cause genetic variation in tissue cultured regenerants. The main goal of the present study was to determine the genetic uniformity of plantlets regenerated through in vitro culture of protocorms, shoot tips, and sodium alginate coated artificial seeds of Cymbidium aloifolium (L.) Sw. and its non-tissue cultured source mother plant using molecular markers such as Random Amplified Polymorphic Deoxyribonucleic acid (RAPD) and Inter Simple Sequence Repeats (ISSR). Ten RAPD and five ISSR primers were used to amplify the genomic DNA isolated from the in vivo plant and randomly selected micropropagated plants. Nine out of ten RAPD primers amplified a total of 256 loci while five ISSR primers amplified a total of 99 loci. The combined data of RAPD and ISSR markers showed low polymorphism. Among the tested plants, dendrograms constructed through UPGMA analysis of RAPD and ISSR markers revealed high genetic similarity between the mother plant and in vitro cultured regenerants. Among the different in vitro regenerants, protocorm-derived plants showed 91% genetic homogeneity to that of the mother plant. Thus, both molecular markers proved to be equally efficient for genetic fidelity studies in C. aloifolium. Hence, this research successfully assessed the genetic fidelity of in vitro cultured plants which could be useful in reintroducing true-to-type plants through plant tissue culture techniques.

Oilseed Brassicas are economically important crops, with Brassica napus, B. juncea, and B. rapa constituting prominent oilseed resources in the Indian subcontinent and across the world. Improving of oil yield, quality, and resistance to abiotic and biotic stresses in oilseed Brassicas warrants concerted efforts. Owing to quantitative nature, the genetic basis of these traits is complex, and can be significantly improved by incorporating the knowledge of precise genetic regulation of these traits. MicroRNAs (miRNAs) can act as attractive targets for crop improvement as they fine-tune gene expression by targeting genes negatively. Here we highlight the emerging evidences of miRNA-mediated regulation of genes controlling several development traits and stress-related traits in oilseed Brassicas. At least 13 miRNAs have so far been well elucidated in oilseed Brassicas using miRNA overexpression, mutation and target mimic approaches, in regulation of different agronomic traits. Further, at least 29 high-throughput small RNA profiling studies have proffered crucial miRNA-target pair candidates for further investigation. This knowledge so far remains unutilized in designing crop improvement programs in oilseed Brassicas. However, there are sufficient evidences to suggest that miRNAs as well as their target genes can be successfully employed in breeding as well as genome editing-mediated engineering of oilseed crops for improving their agricultural traits.