Trehalose biosynthesis is involved in sporulation of Stagonospora nodorum

Abstract

Stagonospora nodorum is a necrotrophic fungal pathogen that is the causal agent of leaf and glume blotch on wheat. S. nodorum is a polycyclic pathogen, whereby rain-splashed pycnidiospores attach to and colonise wheat tissue and subsequently sporulate again within 2-3weeks. As several cycles of infection are needed for a damaging infection, asexual sporulation is a critical phase of its infection cycle. A non-targeted metabolomics screen for sporulation-associated metabolites identified that trehalose accumulated significantly in concert with asexual sporulation both in vitro and in planta. A reverse-genetics approach was used to investigate the role of trehalose in asexual sporulation. Trehalose biosynthesis was disrupted by deletion of the gene Tps1, encoding a trehalose 6-phosphate synthase, resulting in almost total loss of trehalose during in vitro growth and in planta. In addition, lesion development and pycnidia formation were also significantly reduced in tps1 mutants. Reintroduction of the Tps1 gene restored trehalose biosynthesis, pathogenicity and sporulation to wild-type levels. Microscopic examination of tps1 infected wheat leaves showed that pycnidial formation often halted at an early stage of development. Further examination of the tps1 phenotype revealed that tps1 pycnidiospores exhibited a reduced germination rate while under heat stress, and tps1 mutants had a reduced growth rate while under oxidative stress. This study confirms a link between trehalose biosynthesis and pathogen fitness in S.nodorum.

Dissecting the role of G-protein signalling in primary metabolism in the wheat pathogen Stagonospora nodorum

“…Considering the huge natural abundance of trehalose in S. nodorum, these fold changes in abundance are noteworthy. The result conclusively supports the results of Lowe et al (2009) in finding that the accumulation of trehalose is correlated with asexual sporulation in S. nodorum.…”

“…Within the mutant strains, no significant change in trehalose abundance occurs between 5 and 10 days p.i. The accumulation of this metabolite has previously been correlated with asexual sporulation in S. nodorum both in vitro and in planta (Lowe et al, 2009). Therefore, constitutive catabolism of trehalose in S. nodorum is consistent with the inability of the mutant strains gna1-35, gba1-6 and gga1-25 to sporulate under these experimental conditions, as trehalose is important for the growth and development of eukaryotic cells (Lowe et al, 2009;Wilson et al, 2007).…”

“…In a previous study by this laboratory, we demonstrated that ongoing cold stress was sufficient to induce moderate levels of asexual sporulation in the mutant strains (Gummer et al, 2012). As previous sporulation studies in S. nodorum have highlighted the role of primary metabolism in this developmental stage (IpCho et al, 2010;Lowe et al, 2009;Solomon et al, 2005Solomon et al, , 2006cTan et al, 2008), metabolomics was again used to dissect the cold-induced response and identify which metabolites are specifically associated with asexual sporulation.…”

“…In a separate study by Lowe et al (2009), trehalose abundance was also linked to asexual sporulation in S. nodorum. Trehalose synthesis was disrupted by deletion of a trehalose 6-phosphate synthase (Tps1) gene, with the resulting tps1 strain possessing a reduced capacity to develop pycnidia and failing to progress into asexual sporulation.…”

“…Trehalose synthesis was disrupted by deletion of a trehalose 6-phosphate synthase (Tps1) gene, with the resulting tps1 strain possessing a reduced capacity to develop pycnidia and failing to progress into asexual sporulation. GC-MS analysis of metabolite extracts of the tps1 strain showed a correlation between trehalose abundance and asexual sporulation both in vitro and in wheat (Lowe et al, 2009).…”