The apocarotenoid metabolite zaxinone regulates growth and strigolactone biosynthesis in rice

Strigolactone and abscisic acid are carotenoid-derived plant hormones. Here the authors describe the identification of zaxinone, a further apocarotenoid metabolite, which down-regulates strigolactone content and is required for normal growth and development in rice

CRISPR/Cas9 editing of endogenous banana streak virus in the B genome of Musa spp. overcomes a major challenge in banana breeding

Jaindra Tirpathi et al. report a strategy for inactivating endogenous banana streak virus sequences in the plantain B genome using CRISPR/Cas9. They show that three-quarters of edited plants had no viral symptoms under stress conditions, providing an improved B genome germplasm for plantain and banana breeding

Nitro-Phenlactone, a Carlactone Analog with Pleiotropic Strigolactone Activities

International audienceStrigolactones (SLs) are novel phytohormones that shape plant architecture by inhibiting shoot branching and regulating root growth, besides their established functions in stimulating seed germination of root-parasitic weeds, such as Striga and Phelipanche species, and inducing hyphal branching in arbuscular mycorrhizal (AM) fungi (Al-Babili and Bouwmeester, 2015). Canonical SLs are divided into strigol- and orobanchol-like subfamilies with a typical structure consisting of a tricyclic (ABC-ring) and a monocyclic lactone (D-ring), which are connected by an enol ether bridge (Figure 1A and Supplemental Figure 1). SLs are synthesized from carotenoids via carlactone, which lacks the B/C-ring (Alder et al., 2012). In Arabidopsis, carlactone (Figure 1A) is converted by MAX1, a member of the CYP711 family, into carlactonoic acid, after methylation, which, can bind to SL receptor (Abe et al., 2014). In rice, a MAX1 homolog, the carlactone oxidase, introduces B/C-rings into carlactone, yielding 4-deoxyorobanchol (Supplemental Figure 1) (Zhang et al., 2014), the precursor of canonical orobanchol-like SLs. SL perception involves an α/β-fold hydrolase (D14 in rice) that acts as a receptor and the SCF-type ubiquitin ligase MAX2 (D3 in rice) that mediates degradation of target proteins, such as members of the SMAX1-LIKE (SMXL; D53 in rice) family of chaperonin-like proteins (Bennett and Leyser, 2014). By interacting with D14 homolog KAI2, MAX2 mediates also signal transduction of karrikins, smoke-derived compounds that act as growth regulators inhibiting hypocotyl growth and inducing seed germination in Arabidopsis but not in root-parasitic weeds (Smith and Li, 2014)

EST-SSR development for Digitaria exilis and its relatives D. iburua and D. longiflora from transcriptome sequences

Digitaria exilis is an important indigenous cereal in West Africa. The first fonio reference transcriptome was released and became a key tool for developing new molecular markers contributing to a better understanding of its genetic diversity. A total of 126 new putative primer pairs were successfully designed in 37,327 unigenes from the D. exilis transcriptome. Thirty-seven primer pairs were randomly selected and tested for their ability to cross-amplify to related species. Clear amplification patterns were observed on 24 primer pairs. Of these, 71, 74 and 35% showed polymorphism in three species: D. exilis, D. longiflora and D. iburua. The transferability from D. exilis was 96% to D. longiflora and 71% to D. iburua. The new SSR markers confirmed the close genetic proximity of D. exilis with D. longiflora and its stronger genetic difference of D. exilis from D. iburua. These markers will be valuable for completing future knowledge on Digitaria evolutionary history, and for testing gene flows between related species