Gene expression analysis of bud burst process in European hazelnut (Corylus avellana L.) using RNA-Seq

Auxin and carbohydrate control flower bud development in Anthurium andraeanum during early stage of sexual reproduction

BACKGROUND

Flower buds of Anthurium andraeanum frequently cease to grow and abort during the early flowering stage, resulting in prolonged planting times and increased commercialization costs. Nevertheless, limited knowledge exists of the mechanism of flower development after initiation in A. andraeanum.

RESULTS

In this study, the measurement of carbohydrate flow and intensity between leaves and flowers during different growth stages showed that tender leaves are strong sinks and their concomitant flowers are weak ones. This suggested that the tender leaves compete with their concomitant flower buds for carbohydrates during the early growth stages, potentially causing the abortion of the flower buds. The analysis of transcriptomic differentially expressed genes suggested that genes related to sucrose metabolism and auxin response play an important role during flower bud development. Particularly, co-expression network analysis found that AaSPL12 is a hub gene engaged in flower development by collaborating carbohydrate and auxin signals. Yeast Two Hybrid assays revealed that AaSPL12 can interact with AaARP, a protein that serves as an indicator of dormancy. Additionally, the application of exogenous IAA and sucrose can suppress the expression of AaARP, augment the transcriptional abundance of AaSPL12, and consequently expedite flower development in Anthurium andraeanum.

CONCLUSIONS

Collectively, our findings indicated that the combination of auxin and sugar signals could potentially suppress the repression of AaARP protein to AaSPL12, thus advancing the development of flower buds in Anthurium andraeanum.

De novo Transcriptome Analysis and Gene Expression Profiling of Corylus Species

Hazelnut (Corylus), which has high commercial and nutritional benefits, is an important tree for producing nuts and nut oil consumed as ingredient especially in chocolate. While Corylus avellana L. (Euro-pean hazelnut, Betulaceae) and Corylus colurna L. (Turkish hazelnut, Betulaceae) are the two common hazelnut species in Europe, C. avellana L. (Tombul hazelnut) is grown as the most widespread hazelnut species in Turkey, and C. colurna L., which is the most important genetic resource for hazelnut breeding, exists naturally in Anatolia. We generated the transcriptome data of these two Corylus species and used these data for gene discovery and gene expression profiling. Total RNA from young leaves, flowers (male and female), buds, and husk shoots of C. avellana and C. colurna were used for two different libraries and were sequenced using Illumina HiSeq4000 with 100 bp paired-end reads. The transcriptome data 10.48 and 10.30 Gb of C. avellana and C. colurna, respectively, were assembled into 70,265 and 88,343 unigenes, respectively. These unigenes were functionally annotated using the TRAPID platform. We identified 25,312 and 27,051 simple sequen-ce repeats (SSRs) for C. avellana and C. colurna, respectively. TL1, GMPM1, N, 2MMP, At1g29670, CHIB1 unigenes were selected for validation with qPCR. The first de novo transcriptome data of C. co-lurna were used to compare data of C. avellana of commercial importance. These data constitute a valuable extension of the publicly available transcriptomic resource aimed at breeding, medicinal, and industrial research studies.

Exploring the tymovirales landscape through metatranscriptomics data

Tymovirales is an order of viruses with positive-sense RNA genomes that mostly infect plants, but also fungi and insects. The number of genome sequences of viruses that could fit this taxon has been growing in the last few years with the extensive use of high-throughput sequencing. Here, we report the discovery of 31 novel viral genome sequences associated with 27 different host plant species, which were hidden in public databases. These viral sequences were identified through homology searches in more than 3,000 plant transcriptomes from the NCBI Sequence Read Archive (SRA) using known tymovirales sequences as queries. Identification, assembly, and curation of raw SRA reads resulted in 29 viral genome sequences with complete coding regions, and two representing partial genomes. Some of the obtained sequences highlight novel genome organizations for members of the order. Phylogenetic analysis showed that six of the novel viruses are related to alphaflexiviruses, 17 to betaflexiviruses, two to deltaflexiviruses, and six to tymovirids. These findings shed new light on the phylogenetic relationships and evolutionary landscape of this group of viruses. Furthermore, this study illustrates the complexity and genome diversity among members of the order and demonstrates that analyzing public SRA data provides an invaluable tool to accelerate virus discovery and refine virus taxonomy.

Systematic analysis of the OFP genes in six Rosaceae genomes and their roles in stress response in Chinese pear (Pyrus bretschneideri)

OVATE family proteins (OFPs) are the plant-specific transcription factors, and have significant functions in regulating plant growth, development and resistance. The OFP genes have been investigated in several plants, but they still lack a systematic analysis of OFP genes in Chinese pear and some other five Rosaceae genomes. Here, 28 PbrOFPs were identified within Chinese pear and compared them with those of other five Rosaceae genomes. Evolutionary tree revealed that all OFP genes from six Rosaceae genomes were divided into eight groups. Seventeen conserved microsynteny regions were detected in Chinese pear genome, suggested that these PbrOFP genes might be considered to have originated from the large-scale duplication events., indicating these PbrOFP genes might contain specialized regulatory mechanisms in these tissues, such as flower, ovary and fruit. Remarkably, two PbrOFP genes (Pbr010426.1 and Pbr010427.1) were up-regulated under Venturia nashicola treatment, and five PbrOFP genes were up-regulated under PEG treatment, suggesting that these genes might play crucial roles in defence to environmental stresses. Our data presented a systematic analysis and might aid in the selection of appropriate PbrOFPs for further functional studies in Chinese pear, especially in response to the mechanism of biotic and abiotic stresses.