BackgroundMembers of the homeodomain-leucine zipper (HD-Zip) gene family encode transcription factors that are unique to plants and have diverse functions in plant growth and development such as various stress responses, organ formation and vascular development. Although systematic characterization of this family has been carried out in Arabidopsis and rice, little is known about HD-Zip genes in maize (Zea mays L.).Methods and FindingsIn this study, we described the identification and structural characterization of HD-Zip genes in the maize genome. A complete set of 55 HD-Zip genes (Zmhdz1-55) were identified in the maize genome using Blast search tools and categorized into four classes (HD-Zip I-IV) based on phylogeny. Chromosomal location of these genes revealed that they are distributed unevenly across all 10 chromosomes. Segmental duplication contributed largely to the expansion of the maize HD-ZIP gene family, while tandem duplication was only responsible for the amplification of the HD-Zip II genes. Furthermore, most of the maize HD-Zip I genes were found to contain an overabundance of stress-related cis-elements in their promoter sequences. The expression levels of the 17 HD-Zip I genes under drought stress were also investigated by quantitative real-time PCR (qRT-PCR). All of the 17 maize HD-ZIP I genes were found to be regulated by drought stress, and the duplicated genes within a sister pair exhibited the similar expression patterns, suggesting their conserved functions during the process of evolution.ConclusionsOur results reveal a comprehensive overview of the maize HD-Zip gene family and provide the first step towards the selection of Zmhdz genes for cloning and functional research to uncover their roles in maize growth and development.

RNA interference (RNAi) is a sequence-specific, posttranscriptional gene silencing (PTGS) process in plants that is mediated by dsRNA homologous to the silenced gene(s). In this study, we report an efficient method to produce dsRNA using a bacterial expression system. Two fragments of the Sugarcane Mosaic Virus (SCMV) CP (coat protein) gene were amplified by RT-PCR, and cloned into the inverted-repeat cloning vector pUCCRNAi. The two recombinant plasmids were transformed individually into E. coli HT115, an RNase-III deficient strain, and dsRNA was induced by isopropyl-β-D: -thiogalactopyranoside (IPTG). The crude extracts of E. coli HT115 containing large amounts of dsRNA were applied to plants as a spray and the experiment confirmed a preventative efficacy. Our findings demonstrated that spraying crude dsRNA-containing extracts inhibited SCMV infection, and the dsRNA derived from an upstream region (CP1) was more effective than was dsRNA derived from a downstream region (CP2) of the SCMV CP gene. The results provide a valuable tool for plant viral control using dsRNA and the PTGS approach.

BURP domain-containing genes comprise a large plant-specific family, yet the functions are very poorly understood, especially in maize (Zea mays) and sorghum (Sorghum vulgare). In this study, 26 BURP family genes in maize (ZmBURP01-15) and sorghum (SbBURP01-11) were identified including the gene structure, phylogenetic relationship, conserved protein motifs and chromosome locations. These genes have diverse exon-intron structures and distinct organization of putative motifs. The distributions of the genes vary: 15 ZmBURP genes are located in maize on five chromosomes, and 11 SbBURP genes in sorghum are on six chromosomes. Based on the phylogenetic analysis of BURP protein sequences from maize, sorghum and other plants, the BURP genes in maize and sorghum were categorized into five subfamilies (RD22-like, PG1β-like, BURP VI, BURP VII and BURP VIII). Transcript level analysis of ZmBURP genes revealed the expression patterns of BURP genes in maize under diffferent stress conditions. The results suggested that only eight ZmBURP genes were responsive to at least one of the stress treatments applied. Among these genes, seven genes (ZmBURP04, ZmBURP05, ZmBURP08, ZmBURP09, ZmBURP12, ZmBURP14, ZmBURP15) were responsive to ABA and cold respectively, two genes (ZmBURP06 and ZmBURP14) were responsive to NaCl. The results presented here provide useful information for further functional analysis of the BURP gene family in maize and sorghum.

Aux/IAA is an important gene family involved in many aspects of growth and development. Aux/IAA proteins are short-lived nuclear proteins that are induced primarily by various phytohormones. In this study, 29 Aux/IAA family genes (CsIAA01-CsIAA29) were identified and characterized in cucumber, including gene structures, phylogenetic relationships, conserved protein motifs and chromosomal locations. These genes show distinct organizational patterns of their putative motifs. The distributions of the genes vary: except for five CsIAA genes in cucumber that were not located, seven CsIAA genes were found on scaffold, while the other 17 CsIAA genes were distributed on seven other chromosomes. Based on a phylogenetic analysis of the Aux/IAA protein sequences from cucumber, Arabidopsis and other plants, the Aux/IAA genes in cucumber were categorized into seven subfamilies. To investigate whether the expression of CsIAA genes is associated with auxin induction, their transcript levels were monitored in seedlings treated with IAA (indole-3-acetic acid), and their expression patterns were analysed by semiquantitative reverse transcription-polymerase chain reaction (RT-PCR). The results showed that 11/29 CsIAA genes were expressed in leaves whether treated with IAA or not and the time course of processing and compared with the control, five CsIAA genes showed low expression only after 60 min treatment with IAA, while 11 genes showed no expression. These results provide useful information for further functional analysis of Aux/IAA gene family in cucumber.

Grape (Vitis vinifera) is one of the most important fruit trees worldwide, and genomics research has played an important role in grape breeding and culture. According to numerous studies in higher plants, homeodomain-leucine zipper (HD-Zip) proteins are a specific class of transcription factors that play an important role in plant development. In this study, bioinformatics methods were used to carry out genome-wide analysis of a complete set of candidate genes encoding HD-Zip proteins in grape, including analysis of the number, physical locations, and encoded amino acid sequences of grape HD-Zip genes, as well as phylogenetic analysis. We identified 31 HD-Zip genes (Vvhdz1-31) in the grape genome, which were categorized into four classes (HDZip I-IV). These HD-Zip proteins contain 20 conserved motifs; their amino acids sequences were deduced. Chromosomal location analysis revealed that these genes are distributed unevenly across all 18 chromosomes. The digital EST expression analyses provided a first glimpse of the expression patterns of HD-Zip genes in grape. The results of this study provide an important theoretical reference for more thorough investigations of HD-Zip genes in grape, as well as studies examining the growth, development, and breeding of grape.