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BackgroundPennycress [Thlaspi arvense L (Brassicaceae)] is being domesticated as a renewable biodiesel feedstock that also provides crucial ecosystems services, including as a nutritional resource for pollinators. However, its flowers produce significantly less nectar than other crop relatives in the Brassicaceae. This study was undertaken to understand the basic biology of the pennycress nectary as an initial step toward the possibility of enhancing nectar output from its flowers.ResultsPennycress flowers contain four equivalent nectaries located extrastaminally at the base of the insertion sites of short and long stamens. Like other Brassicaceae, the nectaries have open stomates on their surface, which likely serve as the sites of nectar secretion. The nectaries produce four distinct nectar droplets that accumulate in concave structures at the base of each of the four petals. To understand the molecular biology of the pennycress nectary, RNA was isolated from ‘immature’ (pre-secretory) and ‘mature’ (secretory) nectaries and subjected to RNA-seq. Approximately 184 M paired-end reads (368 M total reads) were de novo assembled into a total of 16,074 independent contigs, which mapped to 12,335 unique genes in the pennycress genome. Nearly 3700 genes were found to be differentially expressed between immature and mature nectaries and subjected to gene ontology and metabolic pathway analyses. Lastly, in silico analyses identified 158 pennycress orthologs to Arabidopsis genes with known enriched expression in nectaries. These nectary-enriched expression patterns were verified for select pennycress loci by semi-quantitative RT-PCR.ConclusionsPennycress nectaries are unique relative to those of other agriculturally important Brassicaceae, as they contain four equivalent nectaries that present their nectar in specialized cup-shaped structures at the base of the petals. In spite of these morphological differences, the genes underlying the regulation and production of nectar appear to be largely conserved between pennycress and Arabidopsis thaliana. These results provide a starting point for using forward and reverse genetics approaches to enhance nectar synthesis and secretion in pennycress.Electronic supplementary materialThe online version of this article (10.1186/s12870-017-1146-8) contains supplementary material, which is available to authorized users.

Sorghum [Sorghum bicolor (L.) Moench] is the fifth most important cereal crop globally by harvested area and production. Its drought and heat tolerance allow high yields with minimal input. It is a promising biomass crop for the production of biofuels and bioproducts. In addition, as an annual diploid with a relatively small genome compared to other C4 grasses, and excellent germplasm diversity, sorghum is an excellent research species for other C4 crops such as maize. As a result, an increasing number of researchers are looking to test the transferability of findings from other organisms such as Arabidopsis thaliana and Brachypodium distachyon to sorghum, as well as to engineer new biomass sorghum varieties. Here, we provide an overview of sorghum as a multipurpose feedstock crop which can support the growing bioeconomy, and monocot research model system. We review what makes sorghum such a successful crop and identify some key traits for future improvement. We assess recent progress in sorghum transformation and highlight how transformation limitations still restrict its widespread adoption. Finally, we summarize available sorghum genetic, genomic, and bioinformatics resources. This review is intended for researchers new to sorghum research, as well as those wishing to include non-food and forage applications into their research.