This document discusses the structure and components of flagella found in motile cells. It describes the basic 9+2 arrangement of microtubules that form the core of eukaryotic flagella, with nine peripheral doublet microtubules surrounding a central pair. The base of the flagellum is comprised of three regions: the flagellum proper, transitional zone, and kinetosome. The kinetosome resembles a cartwheel and anchors the flagellum, with nine microtubule triplets that convert to doublets in the flagellum proper.

1. Anurag Kerketta
ID- 130116064
Plant Pathology

2.  Thin hair like delicate structure.
 Found in lower and aquatic fungi.

3.  Forming the core of the flagellum is a central or axial filament known as the
axoneme (A- C).
 The axoneme is surrounded by a double cytoplasmic sheath or membrane
which is an extension of the plasma membrane of the motile cell.

4.  Of these, two are central and nine peripheral. The two central single fibrils
lie side by side and form an elastic axial thread which is sometimes
enclosed by a subsidiary sheath of Its own.
 Of the nine peripheral fibrils, each consists of two thin fibrils.
 The nine peripheral doublet fibrils surround the central pair of singlet fibrils.
 The entire growth of 9+2 fibrils is enclosed by a double cytoplasmic sheath.
This 9+2 arrangement of fibrils is the basic structure of a eukaryotic
flagellum found in the motile cells of all organisms except the bacteria.

5.  The base of the axoneme comprises three regions, the flagellum
proper, the transitional zone and the kinetosome.
 In section, the kinetosome resembles a cartwheel (Fig. 6.2f),
because to each of the nine outer microtubule doublets seen in the
flagellum proper, a third microtubule is attached.
 This is called the C-tubule; in the doublets, that tubule with
extended dynein arms is the A-tubule, and its partner is labelled B.
 These flagellar microtubules radiate as kinetosome props into the
zoospore, perhaps providing structural support and anchorage of
the flagellum (D. J. S. Barr, 2001)

6. Fig. (A) Base of axoneme. (B) TS near Transitional Plate. (C) TS in lower portion of
Transitional Zone. (D) TS of Flagellum props. (E) Schematic drawing of the
flagellum props in TS. (F) Kinetosome in TS.
Source: Webster and Weber, 2007

7.  Microtubules may also be attached laterally to the kinetosome, contributing
to the flagellar root system.
 In the innermost (proximal) part of the transitional zone, the nine
microtubule triplets of the kinetosome are converted into the doublets of the
flagellum proper; concentric fibres, possibly arranged helically, surround the
nine doublet pairs.
 Also within the transitional zone, the two central microtubules arise near a
terminal plate. (Barr & De’saulniers, 1988).

8.  Rao, V. K., Jayalaxmi, R. S., Verma, P. K. and Naidu, V. D. 2011.
Introduction to plant pathogens. Acharya N. G. Ranga Agricultural
University Rajendranagar, Hyderabad. Pp. 23.
 Webster, J. and Weber, R. W. S. 2007. Introduction to fungi. 3rd
edition, Cambridge University Press, Cambridge, New York,
Melbourne, Madrid, Cape Town, Singapore, São Paulo. Pp. 130-
131.