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Serendipita indica (former Piriformospora indica) is a non-obligate endophytic fungus and generally a plant growth and defence promoter with high potential to be used in agriculture. However, S. indica may switch from biotrophy to saprotrophy losing its plant growth promoting traits. Our aim was to understand if the free-living stage growth conditions (namely C availability) regulate S. indica’s phenotype, and its potential as plant-growth-promoting-microbe (PGPM). We grew S. indica in its free-living stage under increasing C availabilities (2–20 g L–1 of glucose or sucrose). We first characterised the effect of C availability during free-living stage growth on fungal phenotype: colonies growth and physiology (plasma membrane proton pumps, stable isotopic signatures, and potential extracellular decomposing enzymes). The effect of the C availability during the free-living stage of the PGPM was evaluated on wheat. We observed that C availability during the free-living stage regulated S. indica’s growth, ultrastructure and physiology, resulting in two distinct colony phenotypes: compact and explorer. The compact phenotype developed at low C, used peptone as the major C and N source, and displayed higher decomposing potential for C providing substrates; while the explorer phenotype developed at high C, used glucose and sucrose as major C sources and casein and yeast extract as major N sources, and displayed higher decomposing potential for N and P providing substrates. The C availability, or the C/N ratio, during the free-living stage left a legacy to the symbiosis stage, regulating S. indica’s potential to promote plant growth: wheat growth promotion by the explorer phenotype was ± 40% higher than that by the compact phenotype. Our study highlights the importance of considering microbial ecology in designing PGPM/biofertilizers. Further studies are needed to test the phenotypes under more extreme conditions, and to understand if the in vitro acquired characteristics persist under field conditions.

Polyamines play a regulatory role in eukaryotic cell growth and morphogenesis. Despite many molecular advances, the underlying mechanism of action remains unclear. Here, we investigate a mechanism by which spermine affects the morphogenesis of a dimorphic fungal model of emerging relevance in plant interactions, Yarrowia lipolytica, through the recruitment of a phytohormone-like pathway involving activation of the plasma membrane P-type H+-ATPase. Morphological transition was followed microscopically, and the H+-ATPase activity was analyzed in isolated membrane vesicles. Proton flux and acidification were directly probed at living cell surfaces by a non-invasive selective ion electrode technique. Spermine and indol-3-acetic acid (IAA) induced the yeast-hypha transition, influencing the colony architecture. Spermine induced H+-ATPase activity and H+ efflux in living cells correlating with yeast-hypha dynamics. Pharmacological inhibition of spermine and IAA pathways prevented the physio-morphological responses, and indicated that spermine could act upstream of the IAA pathway. This study provides the first compelling evidence on the fungal morphogenesis and colony development as modulated by a spermine-induced acid growth mechanism analogous to that previously postulated for the multicellular growth regulation of plants.

O presente trabalho teve como objetivo inventariar e elaborar descrições e ilustrações para as espécies de Orchidaceae encontradas em um fragmento de Floresta Semidecídua localizado no sul do Estado do Espírito Santo, região de poucos estudos, caracterizando uma flora ainda pouco conhecida. Durante o estudo, 25 espécies distribuídas em 21 gêneros, foram registradas. A forma de vida predominante foi a epifítica, caracterizada por 16 espécies, seguida pela rupícola, terrícola e micoheterotrófica. A maior parte das espécies floresceu no período quente e úmido. Além disso, o estudo revelou a presença de uma espécie endêmica e três novas ocorrências para o Estado.

O presente trabalho teve como objetivo inventariar e elaborar descrições e ilustrações para as espécies de Orchidaceae encontradas em um fragmento de Floresta Semidecídua localizado no sul do Estado do Espírito Santo, região de poucos estudos, caracterizando uma flora ainda pouco conhecida. Durante o estudo, 25 espécies distribuídas em 21 gêneros, foram registradas. A forma de vida predominante foi a epifítica, caracterizada por 16 espécies, seguida pela rupícola, terrícola e micoheterotrófica. A maior parte das espécies floresceu no período quente e úmido. Além disso, o estudo revelou a presença de uma espécie endêmica e três novas ocorrências para o Estado.