  Aims. To make a detailed study of the nulling and subpulse drifting in PSR
J1727$-$2739 for investigation of its radiation properties. Methods. The
observations were carried out on 20 March, 2004 using the Parkes 64-m radio
telescope, with a central frequency of 1518 MHz. A total of 5568 single pulses
were analysed. Results. This pulsar shows well defined nulls with lengths
lasting from 6 to 281 pulses and separated by burst phases ranging from 2 to
133 pulses. We estimate a nulling fraction of around 68\%. No emission in the
average pulse profile integrated over all null pulses is detected with
significance above $3\sigma$. Most transitions from nulls to bursts are within
a few pulses, whereas the transitions from bursts to nulls exhibit two patterns
of decay: decrease gradually or rapidly. In the burst phase, we find that there
are two distinct subpulse drift modes with vertical spacing between the drift
bands of $9.7 \pm 1.6$ and $5.2 \pm 0.9$ pulse periods, while sometimes there
is a third mode with no subpulse drifting. Some mode transitions occur within a
single burst, while others are separated by nulls. Different modes have
different average pulse profiles. Possible physical mechanisms are discussed.
