Yeast nitrogen utilization in the phyllosphere during plant lifespan under regulation of autophagy

Abstract

Recently, microbe-plant interactions at the above-ground parts have attracted great attention. Here we describe nitrogen metabolism and regulation of autophagy in the methylotrophic yeast Candida boidinii, proliferating and surviving on the leaves of Arabidopsis thaliana. After quantitative analyses of yeast growth on the leaves of A. thaliana with the wild-type and several mutant yeast strains, we showed that on young leaves, nitrate reductase (Ynr1) was necessary for yeast proliferation, and the yeast utilized nitrate as nitrogen source. On the other hand, a newly developed methylamine sensor revealed appearance of methylamine on older leaves, and methylamine metabolism was induced in C. boidinii, and Ynr1 was subjected to degradation. Biochemical and microscopic analysis of Ynr1 in vitro during a shift of nitrogen source from nitrate to methylamine revealed that Ynr1 was transported to the vacuole being the cargo for biosynthetic cytoplasm-to-vacuole targeting (Cvt) pathway, and degraded. Our results reveal changes in the nitrogen source composition for phyllospheric yeasts during plant aging, and subsequent adaptation of the yeasts to this environmental change mediated by regulation of autophagy.

Pantothenate auxotrophy of Methylobacterium spp. isolated from living plants

“…Phyllosphere microorganisms utilize various nutrient compounds present on plant leaves for their growth and survival in the phyllosphere. For example, methanol and sugar compounds, including glucose, can be utilized as carbon sources, and nitrate and methylamine can be utilized as nitrogen sources [3,5,6,35]. However, it was unknown how phyllosphere microorganisms utilize low molecular compounds that function as cofactors or vitamins in the phyllosphere.…”

“…The presence of sugar compounds including glucose on the leaf surface has also been reported [5]. In addition to these compounds, nitrate, methylamine, and amino acids, which can be used as nitrogen sources, and some trace cofactors like vitamins, have also been reported to be present on the leaf surface [6,7].…”

Phyllospheric Microbiomes: Diversity, Ecological Significance, and Biotechnological Applications

“…The arrangement of leaf epidermal cells describes the leaf physiology and the microenvironment which allow the abundance and distributions of microorganisms on the leaf surface (Shiraishi et al 2015;Esser et al 2015). Simply, epiphytes make biofilm-like growth, most preferably larger bacterial aggregates are on the trichomes, veins, and epidermal cell groves (Brewer et al 1991;Morris et al 1997), where the leaf exudates containing nutrient-rich region.…”

“…The leaf physiology determines the microbial diversity and abundance on the phyllosphere. It establishes the microhabitat where the microorganisms adapt to their physiology to survive in this habitat (Staley et al 2014;Shiraishi et al 2015). The epiphytic microbes formed as colonial form, which gives protection to the microorganisms from this harsh microhabitat (Lindow and Brandl 2003; Remus-Emsermann (Morris et al 1997;Hirano and Upper 2000).…”

Yeast Hog1 proteins are sequestered in stress granules during high-temperature stress

“…The methylotrophic yeast Candida boidinii survives and proliferates on growing plant leaves, assimilating methanol and nitrate for its survival (Kawaguchi et al, 2011;Shiraishi et al, 2015). Therefore, C. boidinii needs to respond and adapt to a wide variety of stresses and environmental changes, including nutrient limitation, high flux of UV radiation, and changes in temperature and osmolarity.…”