Alongside revealing Android M's actual name, and releasing the new Android 6.0 SDK, Google has announced that developers can now submit apps that use Marshmallow's API 23. This means developers can now build their apps against the official SDK, and submit them for testing on Developer Preview devices.

Google Play is now ready to accept your API 23 apps via the Google Play Developer Console on all release channels (Alpha, Beta & Production). At the consumer launch this fall, the Google Play store will also be updated so that the app install and update process supports the new permissions model for apps using API 23.

With this, app developers can begin adding official support for the new features like auto-backup and app permissions, though those features won't start working until we see official Android 6.0 Marshmallow hardware — AKA the next Nexus — in the wild. If you are a developer and plan to submit your app with API 23 features soon, be sure to let us know all about it!

Source: Android Developers