International audience | Flowering plants possess self-incompatibility (SI) mechanisms that promote outbreeding and thereby increase their genetic diversity. In the self-incompatible Brassicaceae, recognition and rejection of self-pollen is based on a receptor-ligand interaction between male and female SI determinants. A transmembrane receptor kinase (S locus Receptor Kinase, SRK) determines the SI specificity in stigmatic cells, whereas a pollen coat-localized ligand (S locus Cysteine-Rich, SCR) determines the SI specificity in pollen. During recent years, major advances have been made in the understanding of the molecular basis of self-pollen recognition by stigmatic cells. In this review, we will focus on evolutionary aspects of the SI system in Brassicaceae. We will describe how the study of the molecular aspect of SI, not only in the historical Brassica model but also in Arabidopsis species, has contributed to highlight certain aspects of evolution of SI in the Brassicaceae.

During the past two years the integrity of Albugo candida as the only species of Albugo parasitic to Brassicaceae has been challenged. The existence of two distinct species parasitic to Brassicaceae has been confirmed, to which a third species was added. For the purpose of further exploring the diversity of the A. candida complex, eight Albugo specimens on Draba lasiocarpa, D. nemorosa, and D. verna (Brassicaceae) were morphologically and molecularly compared with other Albugo species. Based on sequence comparisons and thorough investigation of the characteristics of the oospores, especially surface ornamentation, Albugo voglmayrii sp. nov., parasitic to Draba nemorosa, is described from five specimens collected in Korea and China. It differs from the previously described species, A. candida, A. koreana, and A. lepidii, by its oospore wall ornamentation. The morphological discrepancy is supported by high genetic distances to other species of Albugo in ITS rDNA and cox2 mtDNA. Albugo specimens from D. lasiocarpa and D. verna were grouped with A. candida, revealing that two distinct species may cause white blister rust on the genus Draba. Therefore, the paradigms that: (1) there is only a single species parasitic to Brassicaceae, that (2) oospore morphology is useful only for distinguishing between largely unrelated species; and (3) in general only one species of Albugo may occur on a single host genus need to be discarded.

A comparative study of antioxidant compounds, flavonoids and vitamin C, and also antioxidant activity was carried out in four species of Brassicaceae vegetables used for salads: watercress (Nasturtium officinale R. Br.), mizuna [Brassica rapa L. subsp. nipposinica (L.H. Bailey) Haneltand], wild rocket [Diplotaxis tenuifolia (L.) DC.], and salad rocket [Eruca vesicaria (L.) Cav.]. The characterization of individual phenolic compounds by HPLC-DAD-MS/MS-ESI in watercress and mizuna completes the polyphenol study previously reported for wild rocket and salad rocket. The qualitative study of flavonoids in watercress leaves showed a characteristic glycosylation pattern with rhamnose at the 7 position. Isorhamnetin 3,7-di-O-glucoside was identified in mizuna leaves and may be considered a chemotaxonomical marker in some B. rapa subspecies. Brassicaceae species showed differences in the quantitative study of flavonoids, and the highest content was detected in watercress leaves. Watercress and wild rocket leaves had the highest content of vitamin C. The antioxidant activity evaluated by different methods (ABTS, DPPH, and FRAP assays) showed a high correlation level with the content of polyphenols and vitamin C. In conclusion, the Brassicaceae leaves studied, watercress, mizuna, wild rocket, and salad rocket, presented a large variability in the composition and content of antioxidant compounds. These baby leaf species are good dietary sources of antioxidants with an important variability of bioactive compounds.

Nitrile compounds, whose presence is not common in honey, have been found in the volatile fraction of a few honey types, their relative amounts being particularly high in honeys commercialized under the Taraxacum label. Among them, 2-methylpropanenitrile, 2-methylbutanenitrile, 3-methylbutanenitrile, 2-butenenitrile (cis- or trans-isomer), 3-butenenitrile and 3-methylpentanenitrile, have been identified for the first time in honeys. Melissopalynological analysis of Taraxacum labelled honeys showed a relatively high pollen contribution of other species flowering in spring, such as Diplotaxis sp. Nitrogen-containing compounds, such as nitriles, thiocyanates and isothiocyanates have been previously described as products of hydrolysis of glucosinolates present in Diplotaxis sp. and other Brassicaceae. The nectar contribution of species belonging to the Brassicaceae family is proposed as the origin of the high relative amount of nitriles in Taraxacum honeys.

The new combination Boechera dentata is proposed to replace the most commonly used B. shortii or Arabis shortii (Brassicaceae) for a species widespread in eastern and central United States and rare in Ontario, Canada. The complex nomenclatural history of the species is presented.

Introduction: The quantity and composition of seed oil affects seed viability and storability and hence the value of a species as a resource for nutrition and plant conservation. Supercritical fluid extraction with carbon dioxide (SFE-CO₂) offers a rapid, environmentally friendly alternative to traditional solvent extraction.Objective: To develop a method using SFE-CO₂ to quantify the seed oil content in a broad range of species with high to low oil contents.Methodology: Seed oil was extracted using SFE-CO₂ from four crop species representing high, medium and low oil content: Helianthus annuus, Asteraceae, with ca. 55% oil; Brassica napus, Brassicaceae, with ca. 50% oil; Glycine max, Fabaceae, with ca. 20% oil; and Pisum sativum, Fabaceae, with ca. 2% oil. Extraction pressures of 5000, 6000 and 7500 psi and temperatures of 40, 60 and 80°C were examined and a second step using 15% ethanol as a modifier included. Oil yields were compared with that achieved from Smalley Butt extraction. The optimised SFE-CO₂ method was validated on six species from taxonomically distant families and with varying oil contents: Swietenia humilis (Meliaceae), Stenocereus thurberi (Cactaceae), Sinapis alba (Brassicaceae), Robinia pseudoacacia (Fabaceae), Poa pratensis (Poaceae) and Trachycarpus fortunei (Arecaceae).Results: The two-step extraction at 6000 psi and 80°C produced oil yields equivalent to or higher than Smalley Butt extraction for all species, including challenging species from the Brassicaceae family.Conclusion: SFE-CO₂ enables the rapid analysis of seed oils across a broad range of seed oil contents.

A total of 142 samples of plants showing symptoms of Turnip mosaic virus (TuMV) were collected from fields planted to Brassicaceae and non-Brassicaceae crops in the southwest Marmora region of Turkey, during the 2004-06 growing seasons. Using enzyme-linked immunosorbent assay (ELISA) TuMV was detected in the main brassica-crop fields of Turkey, with an overall incidence of 13·4%. TuMV was detected in samples from Brussels sprouts, cabbage, wild mustard, radish and wild radish, but not cauliflower or broccoli. The full-length sequences of the genomic RNAs of two biologically distinct isolates, TUR1 and TUR9, were determined. Recombination analyses showed that TUR1 was an intralineage recombinant, whereas TUR9 was a non-recombinant. Phylogenetic analyses of the Turkish isolates with those from the rest of the world showed that the TUR1 and TUR9 isolates belonged to world-Brassica and Asian-Brassica/Raphanus groups, respectively. This study showed that TuMV is widely distributed in the Asia Minor region of Turkey.

Plants develop various endoplasmic reticulum (ER)-derived structures, each of which has specific functions. The ER body found in Arabidopsis thaliana is a spindle-shaped structure that specifically accumulates high levels of PYK10/BGLU23, a β-glucosidase that bears an ER-retention signal. The molecular mechanisms underlying the formation of the ER body remain obscure. We isolated an ER body-deficient mutant in Arabidopsis seedlings that we termed nai2. The NAI2 gene (At3g15950) encodes a member of a unique protein family that is only found in the Brassicaceae. NAI2 localizes to the ER body, and a reduction in NAI2 gene expression elongates ER bodies and reduces their numbers. NAI2 deficiency does not affect PYK10 mRNA levels but reduces the level of PYK10 protein, which becomes uniformly diffused throughout the ER. NAI1, a transcription factor responsible for ER body formation, regulates NAI2 gene expression. These observations indicate that NAI2 is a key factor that enables ER body formation and the accumulation of PYK10 in ER bodies of ARABIDOPSIS: Interestingly, ER body-like structures are also restricted to the Brassicales, including the Brassicaceae. NAI2 homologs may have evolved specifically in Brassicales for the purpose of producing ER body-like structures.

The knowledge of the dynamics of inorganic N in soil may help to establish the most suitable timing for green manure (GM) incorporation, which leads to the improvement of crop N use efficiency in conventional as well as organic agriculture. The practice of green manuring with crop species belonging to the Brassicaceae family has recently expanded, in Italy and abroad, due to their demonstrated biocidal effect against soil-borne pathogens. In this plot-scale study we monitored the release of soil inorganic N in 3 soil types (1 clay and 2 loams), in the months following late-spring green manuring with plant material from Brassica juncea, Sinapis alba, and Raphanus sativus species. Soil inorganic N content increased and reached a maximum 2 months after GM incorporation (+14.4 mg N kg1 dry soil, on average, over the initial inorganic N content), and subsequently declined. The inorganic N accumulation was higher in soil amended with R. sativus. We did not observe any significant influence of the soil type on the variation of inorganic N content in the period after GM incorporation. The inorganic N released after late-spring green manuring with Brassicaceae species may become available in the early growth phase of subsequent summer-autumn crops.

The genes FLORICAULA (FLO) in snapdragon and LEAFY (LFY) in arabidopsis encode a key transcription factor in control of the identity of shoot apical meristem, floral transition, and florogenesis. There is a persistent question whether these diverse functions are controlled by one and the same gene or rather, they are distributed between the paralogs arising from gene duplication. Due to its extensive polymorphism, the second intron of FLO/LFY (FLint2) would present a workable model for exploring this problem. We compared FLint2 structures within the genus Brassica and in the family Brassicaceae as a whole. The analysis of already cloned polymorphic regions within FLint2 sequences in diploid (genomes A, B, and C) and allotetraploid (genomes AB, AC, and BC) species of Brassica let us believe that two FLO/LFY paralogs were found within the genome B. All together, the structural polymorphisms, including the presence/absence of the binding site for the transcription regulator AGAMOUS-LIKE3/SEPALLATA4, presume that several Brassicaceae species comprise two FLO/LFY loci. The FLint2-derived markers of FLO/LFY developed in this study will help assess the copy numbers of this gene and carry out a detailed locus-specific analysis of FLint2 structure in diverse Brassica forms.