Growth, Differentiation and Sexuality

3 Mitosis in Filamentous Fungi
S.D. Harris 1
CONTENTS
I. Introduction ......................... 37
II. Fungal Mitosis ........................ 37
A. Chromosome and Spindle Organization . 37
B. TheDuplicationCycle ............... 38
III. Regulation of Mitotic Entry .............. 39
A. TheCDKModule................... 39
B. NimAKinase ...................... 40
IV. Regulation of Mitotic Exit ............... 41
A. Anaphase-PromotingComplex ........ 41
B. TheSIN/MENPathway............... 42
C. γ-Tubulin ......................... 42
D. BimG ............................ 42
V. Mitotic and Post-Mitotic Functions
of Motor Proteins ..................... 43
A. MotorProteinsandMitosis ........... 43
B. Post-Mitotic Nuclear Movement . ...... 43
VI. Coordination of Mitotic Events
in a Multinucleate Hyphal Cell ........... 44
VII. Coordination of Mitosis
with Branch Formation ................. 45
VIII. Regulation of Mitosis in Response
to DNA Damage and Replication Stress .... 45
IX. Regulation of Mitosis in Response
to Spindle Damage .................... 47
X. Future Challenges ..................... 47
A. What Is the Critical Function of NimA
in the Regulation of Mitotic Entry? . . . . . 47
B. How Is Mitotic Exit Coordinated
withCytokinesis?................... 47
C. How Is Nuclear Autonomy Established
inaMultinucleateHyphalCell? ........ 48
D. HowIsMitoticRegulationAltered
byDevelopmentalSignals?............ 48
References ........................... 48
I. Introduction
The cell cycle is a fundamental feature of all dividing
cells (Murray and Hunt 1993). It comprises
the orderly series of events that lead to the duplication
(DNA replication) and segregation (mitosis)
of a cell’s chromosomes. Through the ability to coordinate
the cell cycle with growth and cytokinesis,
1 Plant Science Initiative and Department of Plant Pathology, University
of Nebraska, N234 Beadle, Lincoln, NE 68588-0660, USA
somatic cells insure the formation of identical duplicate
progeny. The dramatic changes in nuclear
morphology that accompany the cell cycle attracted
the interest of early microscopists (cf. Nurse 2000),
which led to a detailed morphological description
of these events. This was particularly true for the
fungi, where, by the early 20th century, descriptive
analyses had already shown that fungal mitoses
were largely identical to those of higher animals
(reviewed by Aist and Morris 1999). However, it
was not until the late 1970s that an understanding
of the molecular mechanisms underlying the fungal
cell cycle began to emerge. This progress was
achieved primarily through genetic and molecular
study of the cell cycle in the yeasts Saccharomyces
cerevisiae and Schizosaccharomyces pombe
(Lew et al. 1997; Su and Yanagida 1997). Most importantly,
these studies confirmed what was previously
hinted at by the earlier microscopic analyses,
namely, that the core biochemistry of the cell cycle
is conserved between fungi and animals. The
advances made using yeast were superbly summarized
in the previous edition of this volume (Mac-
Neill 1994). In this edition, emphasis is placed on
describing progress toward understanding mitosis
in the filamentous fungi. Much has been learned
over the past decade, including important similarities
and key differences with yeast. Notable distinctions
from yeast include insights into the regulation
of mitosis within the context of multinucleate cells
and elaborate morphogenetic programs. The new
results are summarized, along with recent findings
that provide a novel perspective on the regulation
of fungal mitosis.
II. Fungal Mitosis
A. Chromosome and Spindle Organization
As recently summarized by Aist and Morris (1999),
the patterns of chromosome movement and spin-
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© Springer-Verlag Berlin Heidelberg 2006