Role of Heat-Shock Proteins in Cellular Function and in the Biology of Fungi

Abstract

Kingdom Fungi encompass a diverse taxonomy involving filamentous and nonfilamentous fungus,which can be classified on the basis of diversity, morphology, growth and development, reproduction, evolution, ability of causing infection, and toxigenicity [1, 2].Throughout the evolution, fungi have developed diverse mode of reproduction and ability to adapt to their environment [3]. Mode of feeding is absorption in fungi, for which they adhere or grow within the substrate in the form of hyphae. During adverse conditions, filamentous growth takes place to allow easier nutrient diffusion by providing large surface area of hyphae. Generally, fungi require warm and humid conditions for growth. Decrease in temperature causes fungal dormancy (spores are resistant to cold), while increasing temperature leads to degradation of fungi [1].Thus, temperature initiates stress responses in fungi, which can be either heat-shock or cold-shock affecting the life cycle and cellular processes. Optimum temperature for growth of various fungi (Histoplasma capsulatum, Aspergillus fumigatus, and Cryptococcus neoformans) is around 37∘C [4, 5]. Increase in temperature generally causes attenuation and ultimately leads to death of the organism [6, 7]. Fungus such as Saccharomyces cerevisiae can grow at higher temperature (41∘C) [8]. In dimorphic fungi (H. capsulatum), morphology and temperature are linked with each other which converts from filamentous to yeast form at elevated temperature and vice versa