ConsensusUpdateTopic

All fields left null will not be updated.

ConsensusUpdateTopicTransactionBody

Field	Type	Description
topicID	TopicID	UNDOCUMENTED
memo	google.protobuf.StringValue	Short publicly visible memo about the topic. No guarantee of uniqueness. Null for "do not update".
expirationTime	Timestamp	Effective consensus timestamp at (and after) which all consensus transactions and queries will fail. The expirationTime may be no longer than MAX_AUTORENEW_PERIOD (8000001 seconds) from the consensus timestamp of this transaction. On topics with no adminKey, extending the expirationTime is the only updateTopic option allowed on the topic. If unspecified, no change.
adminKey	Key	Access control for update/delete of the topic. If unspecified, no change. If empty keyList - the adminKey is cleared.
submitKey	Key	Access control for ConsensusService.submitMessage. If unspecified, no change. If empty keyList - the submitKey is cleared.
autoRenewPeriod	Duration	The amount of time to extend the topic's lifetime automatically at expirationTime if the autoRenewAccount is configured and has funds (once autoRenew functionality is supported by HAPI). Limited to between MIN_AUTORENEW_PERIOD (6999999 seconds) and MAX_AUTORENEW_PERIOD (8000001 seconds) by servers-side configuration (which may change). If unspecified, no change.
autoRenewAccount	AccountID	Optional account to be used at the topic's expirationTime to extend the life of the topic. Once autoRenew functionality is supported by HAPI, the topic lifetime will be extended up to a maximum of the autoRenewPeriod or however long the topic can be extended using all funds on the account (whichever is the smaller duration/amount). If specified as the default value (0.0.0), the autoRenewAccount will be removed. If unspecified, no change.
memo	string	The memo associated with the topic (UTF-8 encoding max 100 bytes)