BackgroundThe plant-specific TCP transcription factor family, which is involved in the regulation of cell growth and proliferation, performs diverse functions in multiple aspects of plant growth and development. However, no comprehensive analysis of the TCP family in watermelon (Citrullus lanatus) has been undertaken previously.ResultsA total of 27 watermelon TCP encoding genes distributed on nine chromosomes were identified. Phylogenetic analysis clustered the genes into 11 distinct subgroups. Furthermore, phylogenetic and structural analyses distinguished two homology classes within the ClTCP family, designated Class I and Class II. The Class II genes were differentiated into two subclasses, the CIN subclass and the CYC/TB1 subclass. The expression patterns of all members were determined by semi-quantitative PCR. The functions of two ClTCP genes, ClTCP14a and ClTCP15, in regulating plant height were confirmed by ectopic expression in Arabidopsis wild-type and ortholog mutants.ConclusionsThis study represents the first genome-wide analysis of the watermelon TCP gene family, which provides valuable information for understanding the classification and functions of the TCP genes in watermelon.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0765-9) contains supplementary material, which is available to authorized users.

Background Soil salinity is one of the major abiotic stress factors that affect crop growth and yield, which seriously restricts the sustainable development of agriculture. Quinoa is considered as one of the most promising crops in the future for its high nutrition value and strong adaptability to extreme weather and soil conditions. However, the molecular mechanisms underlying the adaptive response to salinity stress of quinoa remain poorly understood. To identify candidate genes related to salt tolerance, we performed reference-guided assembly and compared the gene expression in roots treated with 300 mM NaCl for 0, 0.5, 2, and 24 h of two contrasting quinoa genotypes differing in salt tolerance. Results The salt-tolerant (ST) genotype displayed higher seed germination rate and plant survival rate, and stronger seedling growth potential as well than the salt-sensitive (SS) genotype under salt stress. An average of 38,510,203 high-quality clean reads were generated. Significant Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways were identified to deeper understand the differential response. Transcriptome analysis indicated that salt-responsive genes in quinoa were mainly related to biosynthesis of secondary metabolites, alpha-Linolenic acid metabolism, plant hormone signal transduction, and metabolic pathways. Moreover, several pathways were significantly enriched amongst the differentially expressed genes (DEGs) in ST genotypes, such as phenylpropanoid biosynthesis, plant-pathogen interaction, isoquinoline alkaloid biosynthesis, and tyrosine metabolism. One hundred seventeen DEGs were common to various stages of both genotypes, identified as core salt-responsive genes, including some transcription factor members, like MYB, WRKY and NAC, and some plant hormone signal transduction related genes, like PYL, PP2C and TIFY10A, which play an important role in the adaptation to salt conditions of this species. The expression patterns of 21 DEGs were detected by quantitative real-time PCR (qRT-PCR) and confirmed the reliability of the RNA-Seq results. Conclusions We identified candidate genes involved in salt tolerance in quinoa, as well as some DEGs exclusively expressed in ST genotype. The DEGs common to both genotypes under salt stress may be the key genes for quinoa to adapt to salinity environment. These candidate genes regulate salt tolerance primarily by participating in reactive oxygen species (ROS) scavenging system, protein kinases biosynthesis, plant hormone signal transduction and other important biological processes. These findings provide theoretical basis for further understanding the regulation mechanism underlying salt tolerance network of quinoa, as well establish foundation for improving its tolerance to salinity in future breeding programs.

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Aim: To explore the potential of whole-plant quinoa (WPQ) as a high-protein source for livestock feed, this study evaluated the effects of additives on the fermentation quality and bacterial community of high-moisture WPQ silage. Methods and Results:High-moisture WPQ was ensiled with one of the following additives: untreated control (C), fibrolytic enzyme (E), molasses (M), LAB inoculant (L), a combination of fibrolytic enzyme and LAB inoculant (EL) and a combination of molasses and LAB inoculant (ML). The fermentation quality and bacterial community after 60 days of ensiling were analysed. Naturally fermented WPQ exhibited acetic acid-type fermentation dominated by enterobacteria, with low lactic acid content (37.0 g/kg DM), and high pH value (5.65), acetic acid (70.8 g/kg DM) and NH 3 -N production (229 g/kg TN). Adding molasses alone or combined with LAB inoculant shifted the fermentation pattern towards increased intensity of lactic acid fermentation, lowering the pH value (<4.56), contents of acetic acid (<46.7 g/kg DM) and NH 3 -N (<140 g/kg TN) and total abundance of enterobacteria (<16.0%), and increasing the lactic acid content (>60.5 g/kg DM), lactic/acetic acid ratio (>1.40) and the relative abundance of Lactobacillus (>83.0%). Conclusions:The results suggested that the lack of fermentable sugar could be the main factor of restricting extensive lactic acid fermentation in WPQ silage.Supplementing fermentable sugar or co-ensiling with materials with high WSC content and low moisture content are expected to be beneficial strategies for producing high-quality WPQ silage.Significance and Impact of Study: High biomass production and high protein content make WPQ to be an ideal forage source for livestock feed. Results of this study revealed the restricting factor for extensive lactic acid fermentation in WPQ silage, which could be helpful in producing high-quality WPQ silage.

Wasabi, horseradish and mustard are popular pungent crops in which the characteristic bioactive hydrolysis of specialized glucosinolates (GSLs) occurs. Although the metabolic pathways of GSLs are well elucidated, how plants have evolved convergent mechanisms to accumulate identical GSL components remains largely unknown. In this study, we discovered that sinigrin is predominantly synthesized in wasabi, horseradish and mustard in Brassicaceae. We de novo assembled the transcriptomes of the three species, revealing the expression patterns of gene clusters associated with chain elongation, side chain modification and transport. Our analysis further revealed that several gene clusters were convergently selected during evolution, exhibiting convergent shifts in amino acid preferences in mustard, wasabi and horseradish. Collectively, our findings provide insights into how unrelated crop species evolve the capacity for sinigrin super-accumulation and thus promise a potent strategy for engineering metabolic pathways at multiple checkpoints to fortify bioactive compounds for condiment or pharmaceutical purposes.