Multiple Translocation of the AVR-Pita Effector Gene among Chromosomes of the Rice Blast Fungus Magnaporthe oryzae and Related Species

Magnaporthe oryzae is the causal agent of rice blast disease, a devastating problem worldwide. This fungus has caused breakdown of resistance conferred by newly developed commercial cultivars. To address how the rice blast fungus adapts itself to new resistance genes so quickly, we examined chromosomal locations of AVR-Pita, a subtelomeric gene family corresponding to the Pita resistance gene, in various isolates of M. oryzae (including wheat and millet pathogens) and its related species. We found that AVR-Pita (AVR-Pita1 and AVR-Pita2) is highly variable in its genome location, occurring in chromosomes 1, 3, 4, 5, 6, 7, and supernumerary chromosomes, particularly in rice-infecting isolates. When expressed in M. oryzae, most of the AVR-Pita homologs could elicit Pita-mediated resistance, even those from non-rice isolates. AVR-Pita was flanked by a retrotransposon, which presumably contributed to its multiple translocation across the genome. On the other hand, family member AVR-Pita3, which lacks avirulence activity, was stably located on chromosome 7 in a vast majority of isolates. These results suggest that the diversification in genome location of AVR-Pita in the rice isolates is a consequence of recognition by Pita in rice. We propose a model that the multiple translocation of AVR-Pita may be associated with its frequent loss and recovery mediated by its transfer among individuals in asexual populations. This model implies that the high mobility of AVR-Pita is a key mechanism accounting for the rapid adaptation toward Pita. Dynamic adaptation of some fungal plant pathogens may be achieved by deletion and recovery of avirulence genes using a population as a unit of adaptation

More rapid polar ozone depletion through the reaction of HOCI with HCI on polar stratospheric clouds

THE direct reaction of HOC1 with HC1, known to occur in liquid water1 and on glass surfaces2, has now been measured on surfaces similar to polar stratospheric clouds3,4 and is shown here to play a critical part in polar ozone loss. Two keys to understanding the chemistry of the Antarctic ozone hole5-7 are, one, the recognition that reactions on polar stratospheric clouds transform HC1 into more reactive species denoted by ClOx(refs 812) and, two, the discovery of the ClO-dimer (C12O2) mechanism that rapidly catalyses destruction of O3(refs 1315). Observations of high levels of OClO and ClO in the springtime Antarctic stratosphere1619 confirm that most of the available chlorine is in the form of ClOx (refs 20, 21). But current photochemical models22,23 have difficulty converting HC1 to ClOx rapidly enough in early spring to account fully for the observations5-7,20,21. Here I show, using a chemical model, that the direct reaction of HOC1 with HC1 provides the missing mechanism. As alternative sources of nitrogen-containing oxidants, such as N2O5 and ClONO2, have been converted in the late autumn to inactive HNO3 by known reactions on the sulphate-layer aerosols24-27, the reaction of HOC1 with HC1 on polar stratospheric clouds becomes the most important pathway for releasing that stratospheric chlorine which goes into polar night as HC1. © 1992 Nature Publishing Group

Cytoskeletal protein kinases: titin and its relations in mechanosensing

Titin, the giant elastic ruler protein of striated muscle sarcomeres, contains a catalytic kinase domain related to a family of intrasterically regulated protein kinases. The most extensively studied member of this branch of the human kinome is the Ca2+–calmodulin (CaM)-regulated myosin light-chain kinases (MLCK). However, not all kinases of the MLCK branch are functional MLCKs, and about half lack a CaM binding site in their C-terminal autoinhibitory tail (AI). A unifying feature is their association with the cytoskeleton, mostly via actin and myosin filaments. Titin kinase, similar to its invertebrate analogue twitchin kinase and likely other “MLCKs”, is not Ca2+–calmodulin-activated. Recently, local protein unfolding of the C-terminal AI has emerged as a common mechanism in the activation of CaM kinases. Single-molecule data suggested that opening of the TK active site could also be achieved by mechanical unfolding of the AI. Mechanical modulation of catalytic activity might thus allow cytoskeletal signalling proteins to act as mechanosensors, creating feedback mechanisms between cytoskeletal tension and tension generation or cellular remodelling. Similar to other MLCK-like kinases like DRAK2 and DAPK1, TK is linked to protein turnover regulation via the autophagy/lysosomal system, suggesting the MLCK-like kinases have common functions beyond contraction regulation

Bumble bees show an induced preference for flowers when primed with caffeinated nectar and a target floral odor

Caffeine is a widely occurring plant defense chemical that occurs in the nectar of some plants, e.g., Coffea or Citrus spp., where it may influence pollinator behavior to enhance pollination. Honey bees fed caffeine form longer lasting olfactory memory associations, which could give plants with caffeinated nectar an adaptive advantage by inducing more visits to flowers. Caffeinated free-flying bees show enhanced learning performance and are more likely to revisit a caffeinated target feeder or artificial flower, although it is not clear whether improved memory of the target cues or the perception of caffeine as a reward is the cause. Here, we show that inexperienced bumble bees (Bombus terrestris) locate new food sources emitting a learned floral odor more consistently if they have been fed caffeine. In laboratory arena tests, we fed bees a caffeinated food alongside a floral odor blend (priming) and then used robotic experimental flowers to disentangle the effects of caffeine improving memory for learned food-associated cues versus caffeine as a reward. Inexperienced bees primed with caffeine made more initial visits to target robotic flowers emitting the target odor compared to control bees or those primed with odor alone. Caffeine-primed bees tended to improve their floral handling time faster. Although the effects of caffeine were short lived, we show that food-locating behaviors in free-flying bumble bees can be enhanced by caffeine provided in the nest. Consequently, there is potential to redesign commercial colonies to enhance bees’ forage focus or even bias bees to forage on a specific crop

Patent nasopalatine ducts: an update of the literature and a series of new cases

PURPOSE The objective of this review is to present an update and summary of clinical findings of cases with a patent nasopalatine duct (NPD) reported in the literature from 1881 to 2016. METHODS Previous articles and reviews about patent NPDs were studied and copies of all original publications were obtained for data verification. Furthermore, a literature search was conducted. In addition, the study sample was complemented with four cases recently seen in our institution. RESULTS Ten out of 67 published cases were to be excluded for this analysis due to misinterpretation or misreporting in previous articles. Overall, 57 cases with NPD patency could be analyzed. Males outnumbered females in a ratio of 2:1. The mean age (when this information was available) was 34.1 ± 17.6 years (range 6-69 years). NPDs were located bilaterally (60%), unilaterally (20%) or centrally (20%). Complete or partial patency was reported in 73.9 and 26.1%, respectively. 74.1% of patients presented a variety of clinical signs and symptoms. The ability of the patient to produce a squeaky or whistling sound was the most frequent clinical finding (23.8%). CONCLUSIONS Caution must be exercised when reading review articles about NPD patency since wrong data have been copied in several subsequent publications. Since epidemiological data are missing with regard to patent NPDs, age and gender predilections are not warranted. Bilateral occurrence and full patency were prevailing features in the evaluated case reports of patent NPDs