MKS and NPHP modules cooperate to establish basal body/transition zone membrane associations and ciliary gate function during ciliogenesis

Meckel-Gruber syndrome (MKS), nephronophthisis (NPHP), and related ciliopathies present with overlapping phenotypes and display considerable allelism between at least twelve different genes of largely unexplained function. We demonstrate that the conserved C. elegans B9 domain (MKS-1, MKSR-1, and MKSR-2), MKS-3/TMEM67, MKS-5/RPGRIP1L, MKS-6/CC2D2A, NPHP-1, and NPHP-4 proteins exhibit essential, collective functions at the transition zone (TZ), an underappreciated region at the base of all cilia characterized by Y-shaped assemblages that link axoneme microtubules to surrounding membrane. These TZ proteins functionally interact as members of two distinct modules, which together contribute to an early ciliogenic event. Specifically, MKS/MKSR/NPHP proteins establish basal body/TZ membrane attachments before or coinciding with intraflagellar transport-dependent axoneme extension and subsequently restrict accumulation of nonciliary components within the ciliary compartment. Together, our findings uncover a unified role for eight TZ-localized proteins in basal body anchoring and establishing a ciliary gate during ciliogenesis, and suggest that disrupting ciliary gate function contributes to phenotypic features of the MKS/NPHP disease spectrum.     

Kiwi fruit PMEI inhibits PME activity,modulates root elongation and induces pollen tube burst in Arabidopsis thaliana

Pectins are major components of primary cell wall that play a crucial role in plant development. After biosynthesis, pectins are secreted in the cell wall by Golgi-derived vesicles under a highly methylesterified form and are de-methylesterified by pectin methylesterases (PME). It is hypothesized that PME might be regulated by pectin methylesterase inhibitor (PMEI). In this paper, we show by isoelectric focalisation and subsequent zymogram that kiwi PMEI was able to inhibit Arabidopsis PME activity by forming a complex. The complexes were stable under a wide range of ionic strength and pH. Moreover, PMEI might be able to form a complex with basic PMEs including three PMEs strongly expressed in root and four PMEs expressed in pollen grains. Finally, exogenous treatment with kiwi PMEI was able to reduce the activity of cell wall resident PMEs with persistent effects such as an increase of the root growth and a dramatic effect on pollen tube stability.     

Negative effects of temperature and atmospheric depositions on the seed viability of common juniper (Juniperus communis)

Background and Aims

Environmental change is increasingly impacting ecosystems worldwide. However, our knowledge about the interacting effects of various drivers of global change on sexual reproduction of plants, one of their key mechanisms to cope with change, is limited. This study examines populations of poorly regenerating and threatened common juniper (Juniperus communis) to determine the influence of four drivers of global change (rising temperatures, nitrogen deposition, potentially acidifying deposition and altering precipitation patterns) on two key developmental phases during sexual reproduction, gametogenesis and fertilization (seed phase two, SP2) and embryo development (seed phase three, SP3), and on the ripening time of seeds.

Methods

In 42 populations throughout the distribution range of common juniper in Europe, 11 943 seeds of two developmental phases were sampled. Seed viability was determined using seed dissection and related to accumulated temperature (expressed as growing degree-days), nitrogen and potentially acidifying deposition (nitrogen plus sulfur), and precipitation data.

Key Results

Precipitation had no influence on the viability of the seeds or on the ripening time. Increasing temperatures had a negative impact on the viability of SP2 and SP3 seeds and decreased the ripening time. Potentially acidifying depositions negatively influenced SP3 seed viability, while enhanced nitrogen deposition led to lower ripening times.

Conclusions

Higher temperatures and atmospheric deposition affected SP3 seeds more than SP2 seeds. However, this is possibly a delayed effect as juniper seeds develop practically independently, due to the absence of vascular communication with the parent plant from shortly after fertilization. It is proposed that the failure of natural regeneration in many European juniper populations might be attributed to climate warming as well as enhanced atmospheric deposition of nitrogen and sulfur.     

Arabinogalactan protein-rich cell walls,paramural deposits and ergastic globules define the hyaline bodies of rhinanthoid Orobanchaceae haustoria

Background and Aims

Parasitic plants obtain nutrients from their hosts through organs called haustoria. The hyaline body is a specialized parenchymatous tissue occupying the central parts of haustoria in many Orobanchaceae species. The structure and functions of hyaline bodies are poorly understood despite their apparent necessity for the proper functioning of haustoria. Reported here is a cell wall-focused immunohistochemical study of the hyaline bodies of three species from the ecologically important clade of rhinanthoid Orobanchaceae.

Methods

Haustoria collected from laboratory-grown and field-collected plants of Rhinanthus minor, Odontites vernus and Melampyrum pratense attached to various hosts were immunolabelled for cell wall matrix glycans and glycoproteins using specific monoclonal antibodies (mAbs).

Key Results

Hyaline body cell wall architecture differed from that of the surrounding parenchyma in all species investigated. Enrichment in arabinogalactan protein (AGP) epitopes labelled with mAbs LM2, JIM8, JIM13, JIM14 and CCRC-M7 was prominent and coincided with reduced labelling of de-esterified homogalacturonan with mAbs JIM5, LM18 and LM19. Furthermore, paramural bodies, intercellular deposits and globular ergastic bodies composed of pectins, xyloglucans, extensins and AGPs were common. In Rhinanthus they were particularly abundant in pairings with legume hosts. Hyaline body cells were not in direct contact with haustorial xylem, which was surrounded by a single layer of paratracheal parenchyma with thickened cell walls abutting the xylem.

Conclusions

The distinctive anatomy and cell wall architecture indicate hyaline body specialization. Altered proportions of AGPs and pectins may affect the mechanical properties of hyaline body cell walls. This and the association with a transfer-like type of paratracheal parenchyma suggest a role in nutrient translocation. Organelle-rich protoplasts and the presence of exceptionally profuse intra- and intercellular wall materials when attached to a nitrogen-fixing host suggest subsequent processing and transient storage of nutrients. AGPs might therefore be implicated in nutrient transfer and metabolism in haustoria.     

Chronic High-Fat Diet Impairs Collecting Lymphatic Vessel Function in Mice

Lymphatic vessels play an essential role in intestinal lipid uptake, and impairment of lymphatic vessel function leads to enhanced adipose tissue accumulation in patients with lymphedema and in genetic mouse models of lymphatic dysfunction. However, the effects of obesity on lymphatic function have been poorly studied. We investigated if and how adipose tissue accumulation influences lymphatic function. Using a lymphatic specific tracer, we performed in vivo near-infrared (NIR) imaging to assess the function of collecting lymphatic vessels in mice fed normal chow or high-fat diet (HFD). Histological and whole mount analyses were performed to investigate the morphological changes in initial and the collecting lymphatic vessels. HFD was associated with impaired collecting lymphatic vessel function, as evidenced by reduced frequency of contractions and diminished response to mechanostimulation. Moreover, we found a significant negative correlation between collecting lymphatic vessel function and body weight. Whole mount analyses showed an enlargement of contractile collecting lymphatic vessels of the hind limb. In K14-VEGF-C mice, HFD resulted in a reduced spreading of the tracer within dermal lymphatic vessels. These findings indicate that adipose tissue expansion due to HFD leads to a functional impairment of the lymphatic vasculature, predominantly in collecting lymphatic vessels.