FUNDC1 regulates mitochondrial dynamics at the ER–mitochondrial contact site under hypoxic conditions

In hypoxic cells, dysfunctional mitochondria are selectively removed by a specialized autophagic process called mitophagy. The ER–mitochondrial contact site (MAM) is essential for fission of mitochondria prior to engulfment, and the outer mitochondrial membrane protein FUNDC1 interacts with LC3 to recruit autophagosomes, but the mechanisms integrating these processes are poorly understood. Here, we describe a new pathway mediating mitochondrial fission and subsequent mitophagy under hypoxic conditions. FUNDC1 accumulates at the MAM by associating with the ER membrane protein calnexin. As mitophagy proceeds, FUNDC1/calnexin association attenuates and the exposed cytosolic loop of FUNDC1 interacts with DRP1 instead. DRP1 is thereby recruited to the MAM, and mitochondrial fission then occurs. Knockdown of FUNDC1, DRP1, or calnexin prevents fission and mitophagy under hypoxic conditions. Thus, FUNDC1 integrates mitochondrial fission and mitophagy at the interface of the MAM by working in concert with DRP1 and calnexin under hypoxic conditions in mammalian cells.     

Phytophthora capsici homologue of the cell cycle regulator SDA1 is required for sporangial morphology,mycelial growth and plant infection

SDA1 encodes a highly conserved protein that is widely distributed in eukaryotic organisms. SDA1 is essential for cell cycle progression and organization of the actin cytoskeleton in yeasts and humans. In this study, we identified a Phytophthora capsici orthologue of yeast SDA1, named PcSDA1. In P. capsici, PcSDA1 is strongly expressed in three asexual developmental states (mycelium, sporangia and germinating cysts), as well as late in infection. Silencing or overexpression of PcSDA1 in P. capsici transformants affected the growth of hyphae and sporangiophores, sporangial development, cyst germination and zoospore release. Phalloidin staining confirmed that PcSDA1 is required for organization of the actin cytoskeleton. Moreover, 4′,6‐diamidino‐2‐phenylindole (DAPI) staining and PcSDA1‐green fluorescent protein (GFP) fusions revealed that PcSDA1 is involved in the regulation of nuclear distribution in hyphae and sporangia. Both silenced and overexpression transformants showed severely diminished virulence. Thus, our results suggest that PcSDA1 plays a similar role in the regulation of the actin cytoskeleton and nuclear division in this filamentous organism as in non‐filamentous yeasts and human cells.     

Cochliomycin A inhibits the larval settlement of Amphibalanus amphitrite by activating the NO/cGMP pathway

Cochliomycin A is a compound with anti-barnacle settlement activity and low toxicity, but the molecular mechanism of the compound is unknown. Here, isobaric tags for the relative or absolute quantitation (iTRAQ) labeling proteomic method were applied to analyze changes in the proteome of Amphibalanus（=Balanus） amphitrite cyprids in response to cochliomycin A treatment. Cochliomycin A affected the cytochrome P450, glutathione S-transferase (GST) and NO/cGMP pathways, among which the NO/cGMP pathway was considered to play a key role in barnacle larval settlement, while the cytochrome P450 and the GST pathways are mainly for detoxification. The results of real-time PCR further suggested the NO/cGMP pathway was activated in response to cochliomycin A. Larval settlement assays revealed that S-methylisothiourea sulfate (SMIS) and 1H-(1,2,4)oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) rescued cyprids from cochliomycin A-induced inhibition of larval settlement. The findings supported the hypothesis that cochliomycin A inhibited barnacle larval settlement by stimulating the NO/cGMP pathway.     

Otolith shape lends support to the sensory drive hypothesis in rockfishes

The sensory drive hypothesis proposes that environmental factors affect both signalling dynamics and the evolution of signals and receivers. Sound detection and equilibrium in marine fishes are senses dependent on the sagittae otoliths, whose morphological variability appears intrinsically linked to the environment. The aim of this study was to understand if and which environmental factors could be conditioning the evolution of this sensory structure, therefore lending support to the sensory drive hypothesis. Thus, we analysed the otolith shape of 42 rockfish species (Sebastes spp.) to test the potential associations with the phylogeny, biological (age), ecological (feeding habit and depth distribution) and biogeographical factors. The results showed strong differences in the otolith shapes of some species, noticeably influenced by ecological and biogeographical factors. Moreover, otolith shape was clearly conditioned by phylogeny, but with a strong environmental effect, cautioning about the use of this structure for the systematics of rockfishes or other marine fishes. However, our most relevant finding is that the data supported the sensory drive hypothesis as a force promoting the radiation of the genus Sebastes. This hypothesis holds that adaptive divergence in communication has significant influence relative to other life history traits. It has already been established in Sebastes for visual characters and organs; our results showed that it applies to otolith transformations as well (despite the clear influence of feeding and depth), expanding the scope of the hypothesis to other sensory structures.     

基于16S基因序列海南产白唇竹叶青蛇的分类地位

为研究海南产白唇竹叶青蛇分类地位,捕捉来自海南岛各地的12个白唇竹叶青蛇样本,并从GenBank下载65个竹叶青蛇的样本序列,以瘤鼻蝮蛇为外群,建立16S系统发育树。系统发育树显示,竹叶青蛇分为多个属的观点具有很大的合理性,白唇竹叶青蛇隶属于帝汶(岛屿)竹叶青蛇属。进一步验证了经典形态学和生物地理学的观点,海南岛产白唇竹叶青与其它地方产白唇竹叶青蛇不存在生殖隔离。