Comparative analysis of salt responsive gene regulatory networks in rice and Arabidopsis

Integrated mRNA and miRNA transcriptome analysis of grape in responses to salt stress

Salt stress is an important factor which may negatively affect plant growth and development. High concentrations of Na⁺ ions can destroy the ion balance in plant somatic cells, as well as destroying cell membranes and forming a large number of reactive oxygen species (ROS) and other damage mechanisms. However, plants have evolved numerous defense mechanisms in response to the damages caused by salt stress conditions. Grape (Vitis vinifera L.), a type of economic crop, is widely planted throughout the world. It has been found that salt stress is an important factor affecting the quality and growth of grape crops. In this study, a high-throughput sequencing method was used to identify the differentially expressed miRNAs and mRNAs in grapes as responses to salt stress. A total of 7,856 differentially expressed genes under the salt stress conditions were successfully identified, of which 3,504 genes were observed to have up-regulated expressions and 4,352 genes had down-regulated expressions. In addition, this study also identified 3,027 miRNAs from the sequencing data using bowtie and mireap software. Among those, 174 were found to be highly conserved, and the remaining miRNAs were less conserved. In order to analyze the expression levels of those miRNAs under salt stress conditions, a TPM algorithm and DESeq software were utilized to screen the differentially expressed miRNAs among different treatments. Subsequently, a total of thirty-nine differentially expressed miRNAs were identified, of which fourteen were observed to be up-regulated miRNAs and twenty-five were down-regulated under the salt stress conditions. A regulatory network was built in order to examine the responses of grape plants to salt stress, with the goal of laying a solid foundation for revealing the molecular mechanism of grape in responses to salt stress.

Computational models for prediction of protein-protein interaction in rice and Magnaporthe grisea

INTRODUCTION

Plant-microbe interactions play a vital role in the development of strategies to manage pathogen-induced destructive diseases that cause enormous crop losses every year. Rice blast is one of the severe diseases to rice Oryza sativa (O. sativa) due to Magnaporthe grisea (M. grisea) fungus. Protein-protein interaction (PPI) between rice and fungus plays a key role in causing rice blast disease.

METHODS

In this paper, four genomic information-based models such as (i) the interolog, (ii) the domain, (iii) the gene ontology, and (iv) the phylogenetic-based model are developed for predicting the interaction between O. sativa and M. grisea in a whole-genome scale.

RESULTS AND DISCUSSION

A total of 59,430 interacting pairs between 1,801 rice proteins and 135 blast fungus proteins are obtained from the four models. Furthermore, a machine learning model is developed to assess the predicted interactions. Using composition-based amino acid composition (AAC) and conjoint triad (CT) features, an accuracy of 88% and 89% is achieved, respectively. When tested on the experimental dataset, the CT feature provides the highest accuracy of 95%. Furthermore, the specificity of the model is verified with other pathogen-host datasets where less accuracy is obtained, which confirmed that the model is specific to O. sativa and M. grisea. Understanding the molecular processes behind rice resistance to blast fungus begins with the identification of PPIs, and these predicted PPIs will be useful for drug design in the plant science community.

Genome-Wide Association Analysis for Salt-Induced Phenotypic and Physiologic Responses in Rice at Seedling and Reproductive Stages

Salinity is one of the main adverse environmental factors severely inhibiting rice growth and decreasing grain productivity. Developing rice varieties with salt tolerance (ST) is one of the most economical approaches to cope with salinity stress. In this study, the salt tolerance of 220 rice accessions from rice diversity panel l (RDP1), representing five subpopulations, were evaluated based on 16 ST indices at both seedling and reproductive stages under salt stress. An apparent inconsistency was found for ST between the two stages. Through a gene-based/tightly linked genome-wide association study with 201,332 single nucleotide polymorphisms (SNPs) located within genes and their flanking regions were used, a total of 214 SNPs related to 251 genes, significantly associated with 16 ST-related indices, were detected at both stages. Eighty-two SNPs with low frequency favorable (LFF) alleles in the population were proposed to hold high breeding potential in improving rice ST. Fifty-four rice accessions collectively containing all these LFF alleles were identified as donors of these alleles. Through the integration of meta-quantitative trait locus (QTL) for ST and the response patterns of differential expression genes to salt stress, thirty-eight candidate genes were suggested to be involved in the regulation of rice ST. In total, the present study provides valuable information for further characterizing ST-related genes and for breeding ST varieties across whole developmental stages through marker-assisted selection (MAS).

Genome-wide investigation and expression analysis of APETALA-2 transcription factor subfamily reveals its evolution, expansion and regulatory role in abiotic stress responses in Indica Rice (Oryza sativa L. ssp. indica)

Rice is an important cereal crop that serves as staple food for more than half of the world population. Abiotic stresses resulting from changing climatic conditions are continuously threating its yield and production. Genes in APETALA-2 (AP2) family encode transcriptional regulators implicated during regulation of developmental processes and abiotic stress responses but their identification and characterization in indica rice was still missing. In this context, twenty-six genes distributed among eleven chromosomes in Indica rice encoding AP2 transcription-factor subfamily were identified and their diverse haplotypes were studied. Phylogenetic analysis of OsAP2 TF family-members grouped them into three clades indicating conservation of clades among cereals. Segmental duplications were observed to be principal route of evolution, supporting the higher positive selection-pressure, which were estimated to be originated about 10.57 to 56.72 million years ago (MYA). Conserved domain analysis and intron-exon distribution pattern of identified OsAP2s revealed their exclusive distribution among the specific clades of the phylogenetic tree. Moreover, the members of osa-miR172 family were also identified potentially targeting four OsAP2 genes. The real-time quantitative expression profiling of OsAP2s under heat stress conditions in contrasting indica rice genotypes revealed the differential expression pattern of OsAP2s (6 genes up-regulated and 4 genes down-regulated) in stress- and genotype-dependent manner. These findings unveiled the evolutionary pathways of AP2-TF in rice, and can help the functional characterization under developmental and stress responses.