No abstract

Dendrobium catenatum has become a rare and endangered medicinal plant due to habitat loss in China. As one of the most important and largest transcription factors, WRKY plays a critical role in response to abiotic stresses in plants. However, little is known regarding the functions of the WRKY family in D. catenatum. In this study, a total of 62 WRKY genes were identified from the D. catenatum genome. Phylogenetic analysis revealed that DcWRKY proteins could be divided into three groups, a division supported by the conserved motif compositions and intron/exon structures. DcWRKY gene expression and specific responses under drought, heat, cold and salt stresses were analyzed through RNA-seq data and RT-qPCR assay. The results showed that these genes had tissue-specificity and displayed different expression patterns in response to abiotic stresses. The expression levels of DcWRKY22, DcWRKY36 and DcWRKY45 were up-regulated by drought stress. Meanwhile, DcWRKY22 was highly induced by heat in roots, and DcWRKY45 was significantly induced by cold stress in leaves. Furthermore, DcWRKY27 in roots and DcWRKY58 in leaves were extremely induced under salt treatment. Finally, we found that all the five genes may function in ABA- and SA-dependent manners. This study identified candidate WRKY genes with possible roles in abiotic stress and these findings not only contribute to our understanding of WRKY family genes, but also provide valuable information for stress resistance development in D. catenatum.

Background Cassava (Manihot esculenta Crantz) is an important food crop known for its high starch content. Polyploid breeding is effective in its genetic improvement, and use of 2n gametes in sexual polyploid breeding is one of the potential methods for cassava breeding and improvement. In our study, the cassava sexual tetraploid (ST), which carries numerous valuable traits, was successfully generated by hybridizing 2n female gametes SC5 (♀) and 2n male gametes SC10 (♂). However, the molecular mechanisms remain unclear. To understand these underlying molecular mechanisms behind the phenotypic alterations and heterosis in ST plants, we investigated the differences in gene expression between polyploids and diploids by determining the transcriptomes of the ST plant and its parents during the tuber root enlargement period. We also compared the characters and transcriptomes of the ST plant with its parents. Results The ST plant was superior in plant height, stem diameter, leaf area, petiole length, plant weight, and root weight than the parent plants, except the leaf number, which was lower. The number of starch granules was higher in the roots of ST plants than those in the parent plants after five months (tuber root enlargement period), which could be due to a higher leaf net photosynthetic rate leading to early filling of starch granules. Based on transcriptome analysis, we identified 2934 and 3171 differentially expressed genes (DEGs) in the ST plant as compared to its female and male parents, respectively. Pathway enrichment analyses revealed that flavonoid biosynthesis and glycolysis/gluconeogenesis were significantly enriched in the ST plants, which might contribute to the colors of petiole (purple-red), root epidermis (dark brown), and tuber starch accumulation, respectively. Conclusions After sexual polyploidization, the phenotype of ST has changed significantly in comparison to their diploid parents, mainly manifest as enlarged biomass, yield, early starch filling, deep colored petiole and root epidermis. The tetraploid plants were also mature early due to early starch grain filling. Owing to enriched flavonoid biosynthesis and glycolysis/gluconeogenesis, they are possibly resistant to adversity stresses and provide better yield, respectively.

Apomixis, or asexual seed formation, is of great value for plant breeding and seed production, and is desirable in modern agriculture, but natural apomixis occurs in cassava at very low frequency. In present study, apomixis was induced by the treatments of female flower buds with 1%, 1.5% and 2% (v/v) dimethyl sulfoxide (DMSO) and the results showed that 1.5% DMSO treatment was most effective for the induction of apomictic seed formation in cassava cultivar SC5 with the highest percentages of fruit set and true apomictic seeds. The germinated seedlings resembled their parents and displayed no morphological characteristics of cassava polyploid. Flow cytometry and chromosome counting showed that these plants were uniform diploids. Analysis of 34 DMSO-induced cassava progenies by the expressed sequence tag-simple sequence repeat (EST-SSR) and sequence-related amplified polymorphism (SRAP) markers showed that three true apomictic seeds were obtained from the group of SC5 treated with 1.5% DMSO.

Background Explored the molecular science of anther development is important for improving productivity and overall yield of crops. Although the role of regulatory RNAs, including long non-coding RNAs (lncRNAs) and microRNAs (miRNAs), in regulating anther development has been established, their identities and functions in Camellia oleifera, an important industrial crop, have yet not been clearly explored. Here, we report the identification and characterization of genes, lncRNAs and miRNAs during three stages of the tropical C. oleifera anther development by single-molecule real-time sequencing, RNA sequencing and small RNA sequencing, respectively. Results These stages, viz. the pollen mother cells stage, tetrad stage and uninucleate pollen stage, were identified by analyzing paraffin sections of floral buds during rapid expansion periods. A total of 18,393 transcripts, 414 putative lncRNAs and 372 miRNAs were identified, of which 5,324 genes, 115 lncRNAs, and 44 miRNAs were differentially accumulated across three developmental stages. Of these, 44 and 92 genes were predicted be regulated by 37 and 30 differentially accumulated lncRNAs and miRNAs, respectively. Additionally, 42 differentially accumulated lncRNAs were predicted as targets of 27 miRNAs. Gene ontology enrichment indicated that potential target genes of lncRNAs were enriched in photosystem II, regulation of autophagy and carbohydrate phosphatase activity, which are essential for anther development. Functional annotation of genes targeted by miRNAs indicated that they are relevant to transcription and metabolic processes that play important roles in microspore development. An interaction network was built with 2 lncRNAs, 6 miRNAs and 10 mRNAs. Among these, miR396 and miR156 family were up-regulated, while their targets, genes (GROWTH REGULATING FACTORS and SQUAMOSA PROMOTER BINDING PROTEIN-LIKE genes) and lncRNAs, were down-regulated. Further, the trans-regulated targets of these lncRNAs, like wall-associated kinase2 and phosphomannose isomerase1, are involved in pollen wall formation during anther development. Conclusions This study unravels lncRNAs, miRNAs and miRNA-lncRNA-mRNA networks involved in development of anthers of the tropical C. oleifera lays a theoretical foundation for further elucidation of regulatory roles of lncRNAs and miRNAs in anther development.