Physiological Characteristics and Comparative Secretome Analysis of Morchella importuna Grown on Glucose, Rice Straw, Sawdust, Wheat Grain, and MIX Substrates

Abstract

Morels (Morchella sp.) are economically important edible macro-fungi, which can grow on various synthetic or semi-synthetic media. However, the complex nutritional metabolism and requirements of these fungi remain ill-defined. This study, based on the plant biomass commonly used in the artificial cultivation of morels, assessed and compared the growth characteristics and extracellular enzymes of Morchella importuna cultivated on glucose, rice straw, sawdust, wheat grain, and a mixture of equal proportions of the three latter plant substrates (MIX). M. importuna could grow on all five tested media but displayed significant variations in mycelial growth rate, biomass, and sclerotium yield on the different media. The most suitable medium for M. importuna was wheat and wheat-containing medium, followed by glucose, while rice straw and sawdust were the least suitable. A total of 268 secretory proteins were identified by liquid chromatography coupled with tandem mass spectrometry detection. Functional classification and label-free comparative analysis of these proteins revealed that carbohydrate-active enzyme (CAZYme) proteins were the predominant component of the secretome of M. importuna, followed by protease, peptidase, and other proteins. The abundances of CAZYme proteins differed among the tested media, ranging from 64% on glucose to 88% on rice straw. The CAZYme classes of glycoside hydrolases and carbohydrate-binding module were enriched in the five secretomes. Furthermore, the enzyme activities of CMCase, lignase, amylase, xylase, pNPCase, and pNPGase were detected during the continuous culture of M. importuna in MIX medium, and the relative expression of the corresponding genes were detected by quantitative real-time PCR. The combined data of growth potential, secretome, extracellular enzyme activity, and gene expression on different substrates inferred that M. importuna was weak in lignocellulose degradation but a good starch decomposer. Specifically, in terms of the degradation of cellulose, the ability to degrade cellulose into oligosaccharides was weaker compared with further degradation into monosaccharides, and this might be the speed-limiting step of cellulose utilization in M. importuna. In addition, M. importuna had a strong ability to decompose various hemicellulose glycosidic bonds, especially α- and β-galactosidase. Only a very few lignin-degradation-related proteins were detected, and these were in low abundance, consistent with the presence of weak lignin degradation ability. Furthermore, the presence of lipase and chitinase implied that M. importuna was capable of decomposition of its own mycelia in vitro. The study provides key data that facilitates a further understanding of the complex nutritional metabolism of M. importuna.

Ultrastructure and Physiological Characterization of Morchella Mitospores and Their Relevance in the Understanding of the Morel Life Cycle

“…Morchella spp. strains are able to easily use a variety of sugars with low molecular weight, but it is more difficult for them to use more complex compounds, such as lignin and cellulose [ 23 ]. In low-fertility cultivation conditions, the growth of vegetative hyphae depended entirely on the nutrients contained in basic culture media or the original inoculation blocks, and the hyphae were weak and unable to form mitospores.…”

“…For example, indoor cultivation in the United States has stagnated after a period of operation, and field cultivation in China has recently also suffered 70% non-profit situations in some areas [ 9 , 10 , 11 , 12 ]. As a consequence, there has recently been a comprehensive promotion of field cultivation based on deep knowledge development of basic biological foundations, such as the identification and characteristics of cultivable varieties [ 12 , 13 , 14 , 15 ], the identification of mating type genes [ 9 , 10 ], the characteristics of heterokaryons [ 16 , 17 , 18 , 19 , 20 , 21 ], nutritional metabolism [ 22 , 23 ] and “omics” technology [ 19 , 24 , 25 , 26 , 27 , 28 , 29 ]. However, key questions related to the life cycle of Morchella remain far from completely understood [ 9 , 10 ].…”

First report from India on identification and domestication of Morchella importuna strain ANI1

“…M. importuna substrate preparation is crucial since our research has shown that it requires varied quantities of nutrients at different phases of growth. Researchers from the past have made similar observations on various growing substrates, they documented varying mycelial growth rates, levels of sclerotial formation, and so on(Cai et al 2021). .…”

Epidemic Identification of Fungal Diseases in Morchella Cultivation across China

“…importuna since 2012 [ 1 , 3 ]. Recent progresses have focused on species classification [ 8 , 9 ], genetic development [ 10 , 11 , 12 , 13 ], life cycle [ 2 , 14 ], nutritional metabolism [ 13 , 15 , 16 ] and multiomics [ 10 , 11 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], but less on cultivation management. Nevertheless, ~70% of the growers were unable to make a steady profit, mainly due to a lack of understanding in species cognition, mating type, growth and development, physiology and nutrition, and field management.…”