Genome-Wide Identification and Comparative Analysis of WOX Genes in Four Euphorbiaceae Species and Their Expression Patterns in Jatropha curcas.

The WUSCHEL-related homeobox (WOX) proteins are widely distributed in plants and play important regulatory roles in growth and development processes such as embryonic development and organ development. Here, series of bioinformatics methods were utilized to unravel the structural basis and genetic hierarchy of WOX genes, followed by regulation of the WOX genes in four Euphorbiaceae species. A genome-wide survey identified 59 WOX genes in Hevea brasiliensis (H. brasiliensis: 20 genes), Jatropha curcas (J. curcas: 10 genes), Manihot esculenta (M. esculenta: 18 genes), and Ricinus communis (R. communis: 11 genes). The phylogenetic analysis revealed that these WOX members could be clustered into three close proximal clades, such as namely ancient, intermediate and modern/WUS clades. In addition, gene structures and conserved motif analyses further validated that the WOX genes were conserved within each phylogenetic clade. These results suggested the relationships among WOX members in the four Euphorbiaceae species. We found that WOX genes in H. brasiliensis and M. esculenta exhibit close genetic relationship with J. curcas and R. communis. Additionally, the presence of various cis-acting regulatory elements in the promoter of J. curcas WOX genes (JcWOXs) reflected distinct functions. These speculations were further validated with the differential expression profiles of various JcWOXs in seeds, reflecting the importance of two JcWOX genes (JcWOX6 and JcWOX13) during plant growth and development. Our quantitative real-time PCR (qRT-PCR) analysis demonstrated that the JcWOX11 gene plays an indispensable role in regulating plant callus. Taken together, the present study reports the comprehensive characteristics and relationships of WOX genes in four Euphorbiaceae species, providing new insights into their characterization.

Genomewide comparative analysis of codon usage bias in three sequenced Jatropha curcas.

Jatropha curcas has recently emerged as an important bioenergy plant which is an ideal alternative for fossil fuels. It is particularly significant to analyse the codon usage bias (CUB) and further evaluate the intraspecific genetic divergence of three J. curcas in Asia, considering its potential economic benefits and various utilities. In the present study, the patterns of CUB were systematically compared, and the factors shaping CUB were identified in all three genomes of J. curcas. Our observations indicate that the preference for A/T nucleotides and A/T ending codons was present in all the three genomes. Moreover, 11 identical high-frequency codons as well as the optimal expression receptor Nicotiana tabacum were confirmed. Besides, it was observed that CUB resulted from the combined effects of natural selection and mutation pressure, while the natural selection was the determining factor. Eventually, similarity indices based on relative synonymous codon usage (RSCU) values implied low intraspecific genetic divergence in three Asian J. curcas. This study provides useful clues for improving the expression level of exogenous genes and optimizing breeding programmes by molecular-assisted breeding in J. curcas.

Genome-wide characterization of bZIP transcription factors and their expression patterns in response to drought and salinity stress in Jatropha curcas.

The basic leucine zipper (bZIP) family is one of the largest families of transcription factors (TFs) in plants and is responsible for various functions, including regulating development and responses to abiotic/biotic stresses. However, the roles of bZIPs in the regulation of responses to drought stress and salinity stress remain poorly understood in Jatropha curcas L., a biodiesel crop. In the present study, 50 JcbZIP genes were identified and classified into ten groups. Cis-element analysis indicated that JcbZIP genes are associated with abiotic stress. Gene expression patterns and quantitative real-time PCR (qRT-PCR) showed that four JcbZIP genes (JcbZIPs 34, 36, 49 and 50) are key resistance-related genes under both drought and salinity stress conditions. On the basis of the results of cis-element and phylogenetic analyses, JcbZIP49 and JcbZIP50 are likely involved in responses to drought and salinity stress; moreover, JcbZIP34 and JcbZIP36 might also play important roles in seed development and response to abiotic stress. These findings advance our understanding of the comprehensive characteristics of JcbZIP genes and provide new insights for functional validation in the further.