Genome-wide identification, classification, and expression analysis of CDPK and its closely related gene families in poplar (Populus trichocarpa)

Calcium-dependent protein kinases (CDPKs) are Ca²⁺-binding proteins known to play crucial roles in Ca²⁺ signal transduction pathways which have been identified throughout plant kingdom and in certain types of protists. Genome-wide analysis of CDPKs have been carried out in Arabidopsis, rice and wheat, and quite a few of CDPKs were proved to play crucial roles in plant stress responsive signature pathways. In this study, a comprehensive analysis of Populus CDPK and its closely related gene families was performed, including phylogeny, chromosome locations, gene structures, and expression profiles. Thirty Populus CDPK genes and twenty closely related kinase genes were identified, which were phylogenetically clustered into eight distinct subfamilies and predominately distributed across fifteen linkage groups (LG). Genomic organization analyses indicated that purifying selection has played a pivotal role in the retention and maintenance of Populus CDPK gene family. Furthermore, microarray analysis showed that a number of Populus CDPK and its closely related genes differentially expressed across disparate tissues and under various stresses. The expression profiles of paralogous pairs were also investigated to reveal their evolution fates. In addition, quantitative real-time RT-PCR was performed on nine selected CDPK genes to confirm their responses to drought stress treatment. These observations may lay the foundation for future functional analysis of Populus CDPK and its closely related gene families to unravel their biological roles.     

Genome-wide identification of the class III aminotransferase gene family in rice and expression analysis under abiotic stress

Aminotransferases are pyridoxal 5′-phosphate-dependent enzymes that play crucial roles in plant growth, development, and responses to abiotic stress. The class III aminotransferase family (ATIII family) is an important subfamily. However, no characterization of rice ATIII genes has been previously reported. Using available rice genome sequence information, we identified 12 japonica and 13 indica ATIII genes that were randomly localized on chromosomes 2, 3, 4, 5, 7, 8, and 11. Information provided by the Plant Genome Duplication Database revealed that four japonica and four indica ATIII genes are the results of segmental duplications, and two japonica and six indica genes resulted from tandem duplications. A phylogenetic analysis of the ATIII genes in japonica, indica and Arabidopsis enabled the classification of the genes into six different groups, and the characteristics were established before the monocot-dicot and japonica–indica split. An analysis of the Ka/Ks, divergence time and average indel length suggested the diverse selection styles of the duplicated gene pairs. Gene structure and motif analyses revealed that the ATIII gene family has experienced extensive divergence. Real-time PCR was performed to examine the expression pattern of the japonica ATIII genes in response to various abiotic stresses including drought, salt, and cold. The results suggested that most of the genes were differentially up- or down-regulated in rice seedlings in response to at least one stress factor, which indicates the key role of the rice ATIII gene family in responding to abiotic stresses. These results provide a basis for elucidating the roles of the ATIII genes and their further functional analysis under abiotic stresses.     

Genome-wide analysis of lectin receptor-like kinase family from Arabidopsis and rice

Lectin receptor-like kinases (LecRLKs) are class of membrane proteins found in higher plants that are involved in diverse functions ranging from plant growth and development to stress tolerance. The basic structure of LecRLK protein comprises of a lectin and a kinase domain, which are interconnected by transmembrane region. Here we have identified LecRLKs from Arabidopsis and rice and studied these proteins on the basis of their expression profile and phylogenies. We were able to identify 32 G-type, 42 L-type and 1 C-type LecRLKs from Arabidopsis and 72 L-type, 100 G-type and 1 C-type LecRLKs from rice on the basis of their annotation and presence of lectin as well kinase domains. The whole family is rather intron-less. We have sub-grouped the gene family on the basis of their phylogram. Although on the basis of sequence the members of each group are closely associated but their functions vary to a great extent. The interacting partners and coexpression data of the genes revealed the importance of gene family in physiology and stress related responses. An in-depth analysis on gene-expression suggested clear demarcation in roles assigned to each gene. To gain additional knowledge about the LecRLK gene family, we searched for previously unreported motifs and checked their importance structurally on the basis of homology modelling. The analysis revealed that the gene family has important roles in diverse functions in plants, both in the developmental stages and in stress conditions. This study thus opens the possibility to explore the roles that LecRLKs might play in life of a plant.     

Genome-wide identification and expression analysis of the TaYUCCA gene family in wheat

Molecular Biology Reports - Auxin is an important endogenous hormone in plants. The YUCCA gene encodes a flavin monooxygenase, which is an important rate-limiting enzyme in the auxin synthesis...     

Genome-wide identification and expression analysis of peach auxin response factor gene families

Plant auxin response factors (ARFs) are involved in plant growth, development and multiple other processes. In this study, the ARF gene family in the peach genome was identified by bioinformatics software and RT-PCR. In total, 18 PpARF candidate genes were found in the peach genome. The DNA-binding and ARF domains, as well as motif III and IV of the PpARF gene family were highly conserved. The phylogenetic analysis revealed that PpARF gene family was divided into five classes: Class I (three members), Class II (four members), Class III (five members), Class IV (three members) and Class V (three members). The results of an intron-exon structure analysis indicated that PpARF gene family members were composed of 2–15 exons. A chromosome mapping analysis revealed that PpARF genes were distributed with different densities over eight chromosomes, with the largest number of PpARF genes on chromosome 1 (four genes), followed by chromosome 4 and 6 (three genes each). Only one gene was located on each of chromosome 3, 7 and 8. A conserved motif analysis revealed that the DNA-binding and ARF domains were observed in all PpARF proteins (except for PpARF18). Class I contained no motifs III or IV (except for PpARF7). RT-PCR results indicated that all of the PpARF genes, with the exception of PpARF15 and PpARF17, were expressed in at least one of the tissues (roots, stems, leaves, flowers and five stages of fruit development). These results suggested that the PpARF gene family members are highly and structurally conserved, and are involved in various aspects of peach growth and development, especially in fruit development.     

Expression of three members of the calcium-dependent protein kinase gene family in Arabidopsis thaliana

Calcium-dependent protein kinases (CDPKs) belong to a unique family of enzymes containing a single polypeptide chain with a kinase domain at the amino terminus and a putative calcium-binding EF hands structure at the carboxyl terminus. From Arabidopsis thaliana, we have cloned three distinct cDNA sequences encoding CDPKs, which were designated as atcdpk6, atcdpk9 and atcdpk19. The full-length cDNA sequences for atcdpk6, atcdpk9 and atcdpk19 encode proteins with a molecular weight of 59343, 55376 and 59947, respectively. Recombinant atCDPK6 and atCDPK9 proteins were fully active as kinases whose activities were induced by Ca²⁺. Biochemical studies suggested the presence of an autoinhibitory domain in the junction between the kinase domain and the EF hands structure. Serial deletion of the four EF hands of atCDPK6 demonstrated that the integrity of the four EF hands was crucial to the Ca²⁺ response. All the three atcdpk genes were ubiquitously expressed in the plant as demonstrated by RNA gel blot experiments. Comparison of the genomic sequences suggested that the three cdpk genes have evolved differently. Using antibodies against atCDPK6 and atCDPK9 for immunohistochemical experiments, CDPKs were found to be expressed in specific cell types in a temporally and developmentally regulated manner.     

Genome-wide identification, phylogeny and expression analysis of the lipoxygenase gene family in cucumber

Plant lipoxygenase (LOX) is involved in growth and developmental control processes, through the biosynthesis of regulatory molecules and defense responses to pathogens, wounding and stress. To date, few LOX proteins and little tissue expression profiling have been reported in detail for cucumber (Cucumis sativus L.). Recent completion of the cucumber genome sequence now permits genome-wide analysis of the LOX gene family in cucumber as well as comparison with LOX in Arabidopsis and rice. We identified 23 candidate LOX genes in the cucumber genome; phylogenetic analysis indicated that these LOX members cluster into two groups, designated types 1 and 2, as expected from previous studies. Sequence analysis showed that five binding sites of iron, including two consensus histidines in the LOX domain, are highly conserved in the cucumber LOX proteins. Analysis of chromosomal localization and genome distribution suggested that tandem duplication and/or polyploidal duplication contributed to the expansion of the cucumber LOX gene family. Based on intron/exon structure analysis, only a few of the extant intron patterns existed in the ancestor of monocots and eudicots. Expression data showed widespread distribution of the cucumber LOX gene family within plant tissues, suggesting that they perform different functions in different tissues.     

Genome-wide identification and characterization of the RIO atypical kinase family in plants

Members of the right open reading frame (RIO) atypical kinase family are present in all three domains of life. In eukaryotes, three subfamilies have been identified: RIO1, RIO2, and RIO3. Studies have shown that the yeast and human RIO1 and RIO2 kinases are essential for the biogenesis of small ribosomal subunits. Thus far, RIO3 has been found only in multicellular eukaryotes. In this study, we systematically identified members of the RIO gene family in 37 species representing the major evolutionary lineages in Viridiplantae. A total of 84 RIO genes were identified; among them, 41 were classified as RIO1 and 43 as RIO2. However, no RIO3 gene was found in any of the species examined. Phylogenetic trees constructed for plant RIO1 and RIO2 proteins were generally congruent with the species phylogeny. Subcellular localization analyses showed that the plant RIO proteins were localized mainly in the nucleus and/or cytoplasm. Expression profile analysis of rice, maize, and Arabidopsis RIO genes in different tissues revealed similar expression patterns between RIO1 and RIO2 genes, and their expression levels were high in certain tissues. In addition, the expressions of plant RIO genes were regulated by two drugs: mycophenolic acid and actinomycin D. Function prediction using genome-wide coexpression analysis revealed that most plant RIO genes may be involved in ribosome biogenesis. Our results will be useful for the evolutionary analysis of the ancient RIO kinase family and provide a basis for further functional characterization of RIO genes in plants.     

Genome-wide identification and analysis of membrane-bound O-acyltransferase (MBOAT) gene family in plants

Membrane bound O-acyl transferase (MBOAT) family is composed of gene members encoding a variety of acyltransferase enzymes, which play important roles in plant acyl lipid metabolism. Here, we present the first genome-enabled identification and analysis of MBOAT gene models in plants. In total, we identified 136 plant MBOAT sequences from 14 plant species with complete genomes. Phylogenetic relationship analyses suggested the plant MBOAT gene models fell into four major groups, two of which likely encode enzymes of diacylglycerol acyltransferase 1 (DGAT1) and lysophospholipid acyltransferase (LPLAT), respectively, with one–three copies of paralogs present in each of the most plant species. A group of gene sequences, which are homologous to Saccharomyces cerevisiae glycerol uptake proteins (GUP), was identified in plants; copy numbers were conserved, with only one copy represented in each of the most plant species; analyses showed that residues essential for acyltransferases were more prone to be conserved than vertebrate orthologs. Among four groups, one was inferred to emerge in land plants and experience a rapid expansion in genomes of angiosperms, which suggested their important roles in adaptation of plants in lands. Sequence and phylogeny analyses indicated that genes in all four groups encode enzymes with acyltransferases. Comprehensive sequence identification of MBOAT family members and investigation into classification provide a complete picture of the MBOAT gene family in plants, and could shed light into enzymatic functions of different MBOAT genes in plants.