8 Molecular Control of Fungal Senescence and Longevity
Research on fungal senescence, in particular on Podospora anserina and Saccharomyces cerevisiae, has unraveled a network of molecular pathways affecting aging and lifespan. The physiological decline of biological systems is linked to impairments of cellul
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Molecular Control of Fungal Senescence and Longevity
MATTHIAS WIEMER1, CAROLIN GRIMM1, HEINZ D. OSIEWACZ1
CONTENTS I. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 II. Molecular Degeneration . . . . . . . . . . . . . . . . . . . . . 156 A. Mitochondrial DNA Instabilities . . . . . . . . . . 156 B. Generation and Function of Reactive Oxygen Species . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 III. Counteracting the Accumulation of Molecular Degeneration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160 A. ROS Scavenging . . . . . . . . . . . . . . . . . . . . . . . . . . 160 B. Repair and Degradation of Molecular Damage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164 C. Mitochondrial Dynamics . . . . . . . . . . . . . . . . . . 167 D. Autophagy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168 E. Replacement and Remodeling of Degraded Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169 VI. Programmed Cell Death . . . . . . . . . . . . . . . . . . . . . 170 VI. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
I. Introduction Fungi are widely thought to be immortal. This view is supported by the description of a huge vegetation body of an Armillaria bulbosa individual in Michigan with an estimated weight of at least 10,000 kg and a current age of approximately 1500 years (Smith et al. 1992). However, there are also species described with a restricted lifespan and defined signs of agerelated degeneration. Historically, the first detailed description of such a phenotype dates back to studies of Rizet in the early 1950s (Rizet 1953a, b). He reported that, during vegetative growth, cultures of the filamentous ascomycete 1
Department of Biosciences, Institute of Molecular Biosciences and Cluster of Excellence Frankfurt Macromolecular Complexes, J W Goethe University, Frankfurt 60438, Germany; e-mail: [email protected]
Podospora anserina change their morphology, slow down growth until it completely ceases, and the hyphae die at their tips. Only some years later Mortimer and Johnson reported that the yeast Saccharomyces cerevisiae does only generate a finite number of daughter cells (Mortimer and Johnston 1959). Subsequently, over the last several decades many other agerelated degenerative processes have been reported in fungi (Bertrand et al. 1985, 1986; Bo¨ckelmann and Esser 1986; Chan et al. 1991; Geydan et al. 2012; Lazarus et al. 1980; Lazarus and Ku¨ntzel 1981). The time-dependent degenerative processes in fungi comply with the general definition of biological aging as a progressive decline of physiological functions (Kirkwood and Austad 2000). The understanding of the underlying mechanisms is of particular interest, because this knowledge is certainly a key toward the development of interventions into degenerative processes. For instan
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