Transcriptome-Based Identification and Expression Profiling of AP2/ERF Members in Caragana Intermedia and Functional Analysis of CiDREB3

Caragana. intermedia Kuang et H.C.Fu., a xerophytic deciduous shrub that widely distributed in arid and semi-arid desert areas of North-west China, is highly tolerant to cold, drought, salt-alkali and barren. In this study, the transcriptome C. intermedia under drought treatment was screened for the genes encoding the AP2/ERF family of transcription factors. As a result, 22 sequences with complete open reading frames (ORFs) were obtained. All sequences were divided into 13 groups, including the DREB A1 to A6, ERF B1 to B6, and RAV groups. The results of multiple sequence alignment (MSA) analysis, domain distribution analysis, conservative motif analysis and tertiary structure prediction showed that all the AP2/ERF transcription factors contained the AP2 domain. The AP2 domain contained the YRG and RAYD elements. In addition, quantitative real-time polymerase chain reaction (qRT-PCR) was employed to analyze the expression patterns of the 22 AP2/ERF transcription factors in C. intermedia. Most of the transcription factors exhibited tissue-specific expression. The expression of most transcription factors was induced to varying degrees by cold, heat, salt and mannitol stress. Furthermore, Heterologous expression of CiDREB3 in transgenic Arabidopsis L. Heynh decreased root length and fresh weight, decreased rosette leaf diameter and number of leaf, and improved drought tolerance during seedlings development. Taken together, the results of the present study help to better understand the functions of the AP2/ERF family of transcription factors in plant responses to multiple abiotic stresses and deeply insight the roles of CiDREB3 in Arabidopsis morphology and conferring abiotic stress tolerance.

Genome-wide investigation of the AP2/ERF gene family in ginger: evolution and expression profiles during rhizome and inflorescence development

Background:AP2/ERF transcription factors perform indispensable functions in various biological processes, such as plant growth, development, biotic and abiotic stresses responses. The AP2/ERF transcription factor family has been identified in many plants, and several AP2/ERF transcription factors from Arabidopsis (Arabidopsis thaliana) have been functionally characterized. However, little research has been conducted on the AP2/ERF genes of ginger (Zingiber officinale), which is an important edible and medicinal horticultural plant. The recently published whole genome sequence of ginger allowed us to study the tissue and expression profiles of AP2/ERF genes in ginger on a genome-wide basis.Results:In this study, 163 AP2/ERF genes of ginger (ZoAP2/ERF) were identified and renamed according to the chromosomal distribution of the ZoAP2/ERF genes. According to the number conserved domains and gene structure, the AP2/ERF genes were divided into three subfamilies by phylogenetic analysis, namely, AP2 (35 members), ERF (125 members) and RAV (3 members). A total of 10 motifs were detected in ginger AP2/ERF genes, and some of the unique motifs were found to be important for the function of ZoAP2/ERF genes.Conclusion:A comprehensive analysis of AP2/ERF gene expression patterns in different tissues and rhizome development stages by transcriptom sequence and quantitative real-time PCR (qRT-PCR) showed that they played an important role in the growth and development of ginger, and genes that might regulate rhizome and flower development were preliminarily identified. This systematic analysis establishes a foundation for further studies of the functional characteristics of ZoAP2/ERF genes and improvement of ginger.

An amiRNA screen uncovers redundant CBF & ERF34/35 transcription factors that differentially regulate arsenite and cadmium responses

Arsenic stress causes rapid transcriptional responses in plants. However, transcriptional regulators of arsenic-induced gene expression in plants remain less well known. To date, forward genetic screens have proven limited for dissecting arsenic response mechanisms. We hypothesized that this may be due to the extensive genetic redundancy present in plant genomes. To overcome this limitation, we pursued a forward genetics screen for arsenite tolerance using a randomized library of plants expressing >2,000 artificial microRNAs (amiRNAs). This library was designed to knock-down diverse combinations of homologous gene family members within sub-clades of transcription factor and transporter gene families. We identified six transformant lines showing an altered response to arsenite in root growth assays. Further characterization of an amiRNA line targeting closely homologous CBF and ERF transcription factors show that the CBF1,2 and 3 transcription factors negatively regulate arsenite sensitivity. Furthermore, the ERF34 and ERF35 transcription factors are required for cadmium resistance. Generation of CRISPR lines, higher-order T-DNA mutants, and gene expression analyses, further support our findings. These ERF transcription factors differentially regulate arsenite sensitivity and cadmium tolerance.

Genome-wide identification and expression analysis of AP2/ERF transcription factors in sugarcane (Saccharum spontaneum L.)

Background APETALA2/ETHYLENE RESPONSIVE FACTOR (AP2/ERF) transcription factors play essential roles in plant growth, development, metabolism, and responses to biotic and abiotic stresses. However, few studies concerning AP2/ERF genes in sugarcane which are the most critical sugar and energy crops worldwide. Results A total of 218 AP2/ERF genes were identified in the Saccharum spontaneum genome. Phylogenetic analysis showed that these genes could be divided into four groups, including 43 AP2s, 160 ERFs and Dehydration-responsive element-binding (DREB) factors, 11 ABI3/VPs (RAV), and four Soloist genes. These genes were unevenly distributed on 32 chromosomes. The structural analysis of SsAP2/ERF genes showed that 91 SsAP2/ERFs lacked introns. Sugarcane and sorghum had a collinear relationship between 168 SsAP2/ERF genes and sorghum AP2/ERF genes that reflected their similarity. Multiple cis-regulatory elements (CREs) present in the SsAP2/ERF promoter were related to abiotic stresses, suggesting that SsAP2/ERF activity could contribute to sugarcane adaptation to environmental changes. The tissue-specific analysis showed spatiotemporal expression of SsAP2/ERF in the stems and leaves of sugarcane at different development stages. In ten sugarcane samples, 39 SsAP2/ERFs were not expressed, whereas 58 SsAP2/ERFs were expressed in all samples. Quantitative PCR experiments showed that SsERF52 expression was up-regulated under salt stress, but suppressed under dehydration stress. SsSoloist4 had the most considerable upregulation in response to treatment with the exogenous hormones ABA and GA. Within 3 h of ABA or PEG6000 treatment, SsSoloist4 expression was up-regulated, indicating that this gene could play a role in the responses to ABA and GA-associated dehydration stress. Analysis of AP2/ERF gene expression patterns under different treatments indicated that SsAP2/ERF genes played an essential role in dehydration and salt stress responses of S. spontaneum. Conclusions In this study, a total of 218 members of the AP2 / ERF superfamily were identified in sugarcane, and their genetic structure, evolution characteristics, and expression patterns were studied and analyzed. The results of this study provide a foundation for future analyses to elucidate the importance of AP2/ERF transcription factors in the function and molecular breeding of sugarcane.