Physiological characterization and genetic modifiers of aberrant root thigmomorphogenesis in mutants of Arabidopsis thaliana MILDEW LOCUS O genes

Root architecture and growth patterns are plant features that are still poorly understood. When grown under in vitro conditions, seedlings with mutations in Arabidopsis thaliana genes MLO4 or MLO11 exhibit aberrant root growth patterns upon contact with hard surfaces, exemplified as tight root spirals. We used a set of physiological assays and genetic tools to characterize this thigmomorphogenic defect in detail. We observed that the mlo4/mlo11‐associated root curling phenotype is not recapitulated in a set of mutants with altered root growth patterns or architecture. We further found that mlo4/mlo11‐conditioned root curling is not dependent upon light and endogenous flavonoids, but is pH‐sensitive and affected by exogenous calcium levels. Based upon the latter two characteristics, mlo4‐associated root coiling appears to be mechanistically different from the natural strong root curvature of the Arabidopsis ecotype Landsberg erecta. Gravistimulation reversibly overrides the aberrant thigmomorphogenesis of mlo4 seedlings. Mutants with dominant negative defects in α‐tubulin modulate the extent and directionality of mlo4/mlo11‐conditioned root coils, whereas mutants defective in polar auxin transport (axr4, aux1) or gravitropism (pgm1) completely suppress the mlo4 root curling phenotype. Our data implicate a joint contribution of calcium signalling, pH regulation, microtubular function, polar auxin transport and gravitropism in root thigmomorphogenesis.     

A new genus and species of hypodermatine bot flies (Diptera: Oestridae)

The bot fly Gruninomyia mira Szpila & Pape, gen.n. , sp.n. is described from Iran, North Khorasan, based on a single adult male and with no larval or host data. The monotypic genus shows a mixture of features otherwise found in either the rodent/lagomorph‐parasitizing oestromyine clade (Oestroderma + Oestromyia) or the artiodactyl‐parasitizing hypodermatine clade (Hypoderma + Pallasiomyia + Pavlovskiata + Przhevalskiana + Strobiloestrus) of subfamily Hypodermatinae. A morphology‐based phylogenetic analysis is marginally in favour of a position of Gruninomyia Szpila & Pape, gen.n. as sister taxon of (Oestroderma + Oestromyia). The COI barcode sequence is provided for the new species, and a phylogenetic analysis based on this marker for Oestridae retrieved from GenBank is in agreement with the conclusions based on morphological data. This published work has been registered in ZooBank: http://zoobank.org/urn:lsid:zoobank.org:pub:8F0CBE07‐4E74‐4186‐B690‐2C97D7ED7DA7 .