Analysis of two in planta expressed LysM effector homologs from the fungus Mycosphaerella graminicola reveals novel functional properties and varying contributions to virulence on wheat.

Secreted effector proteins enable plant pathogenic fungi to manipulate host defenses for successful infection. Mycosphaerella graminicola causes Septoria tritici blotch disease of wheat (Triticum aestivum) leaves. Leaf infection involves a long (approximately 7 d) period of symptomless intercellular colonization prior to the appearance of necrotic disease lesions. Therefore, M. graminicola is considered as a hemibiotrophic (or necrotrophic) pathogen. Here, we describe the molecular and functional characterization of M. graminicola homologs of Ecp6 (for extracellular protein 6), the Lysin (LysM) domain-containing effector from the biotrophic tomato (Solanum lycopersicum) leaf mold fungus Cladosporium fulvum, which interferes with chitin-triggered immunity in plants. Three LysM effector homologs are present in the M. graminicola genome, referred to as Mg3LysM, Mg1LysM, and MgxLysM. Mg3LysM and Mg1LysM genes were strongly transcriptionally up-regulated specifically during symptomless leaf infection. Both proteins bind chitin; however, only Mg3LysM blocked the elicitation of chitin-induced plant defenses. In contrast to C. fulvum Ecp6, both Mg1LysM and Mg3LysM also protected fungal hyphae against plant-derived hydrolytic enzymes, and both genes show significantly more nucleotide polymorphism giving rise to nonsynonymous amino acid changes. While Mg1LysM deletion mutant strains of M. graminicola were fully pathogenic toward wheat leaves, Mg3LysM mutant strains were severely impaired in leaf colonization, did not trigger lesion formation, and were unable to undergo asexual sporulation. This virulence defect correlated with more rapid and pronounced expression of wheat defense genes during the symptomless phase of leaf colonization. These data highlight different functions for MgLysM effector homologs during plant infection, including novel activities that distinguish these proteins from C. fulvum Ecp6.

Identification and characterisation of Mycosphaerella graminicola secreted or surface-associated proteins with variable intragenic coding repeats.

Pathogenic micro-organisms have been suggested to vary the number of intragenic repeats present within secreted or cell membrane/cell wall-associated proteins in order to manipulate host immune responses. We have identified a number of genes predicted to encode secreted proteins possessing internal tandem repeats in the genome sequence of Mycosphaerella graminicola (isolate IPO323), a wheat leaf-specific fungal pathogen and causal agent of Septoria tritici blotch disease. Twenty-three M. graminicolaTandem Repeat Proteins (MgTRPs) were subject to further analysis. Many MgTRPs varied in the number of intragenic repeats between isolates and almost all were expressed. Peak gene expression was frequently observed towards the end of the symptomless phase of wheat leaf colonisation which typically lasts for 8-10 days after inoculation. In contrast, with one exception, increased expression of the majority of MgTRPs was not detected during interactions with resistant host genotypes. Repeat number differences detected in genomic DNA were retained in different transcript sizes produced during plant infection by different isolates. One in planta expressed MgTRP was found to reside within a approximately 6 kb region that appears to be absent from a number of tested isolates and also from individual members of a modern field population. Sequence analysis of another in planta expressed MgTRP from six isolates highlighted the potential for structural changes which may occur as a consequence of varying internal repeat numbers and provided support for repeat variation occurring as a consequence of intragenic recombination. These data provide new insights into the genetic variation which exists within M. graminicola populations at the level of in planta expressed secreted/surface-associated proteins which are candidate effectors in the host-pathogen interaction.

An historical analysis of the role of paintings and photographs in comforting bereaved parents.

OBJECTIVE: To examine the place of recent and historical pictorial representations of the dead baby and their relevance to the current care of grieving parents. DESIGN: A selective review of the literature on representations of the dead baby. Visual examination of seven paintings (1550-1676) in order to understand their meaning. FINDINGS: In the late 20th century the practice of taking photographs of the baby who had died became widely accepted. In the 16th and 17th centuries grief at the loss of a baby could be portrayed in the form of paintings. There are similarities between photographs currently being produced and the paintings produced four centuries ago. At both times grief could be expressed through religious rites and naming the child. Although some portrayals have been naturalistic, this has often not been the case. Paintings gave parents an opportunity to 'count' the child as part of the family. KEY CONCLUSIONS: These paintings suggest that a practice recommended as innovative in the late 20th century may have had a long history. Historically, families had a healthier attitude towards the death of a baby than in the mid-20th century. It is suggested that the difficulty of facing death, on which midwifery care of the grieving mother was, until recently, based may have been a temporary aberration. IMPLICATIONS FOR PRACTICE: The sensitive care of the grieving parents has a long and well-authenticated history.