After breaking into Edinburgh's first XV at the beginning of the 2017/18 season, Johnstone signed a two-year deal to remain at the club on a full-time basis.
A former Scotland Sevens star, Johnstone burst onto the World Series Sevens circuit in 2013.
The abrasive centre represented Scotland at the Rugby World Cup 7s in Moscow that same year before competing in the Glasgow 2014 Commonwealth Games.
He finished Scotland’s second highest try-scorer for the season in 2015/16, crossing the whitewash on 22 occasions and played a pivotal role in Scotland’s historic Cup win in the final leg of the 2015/16 Series in London. He has amassed a staggering 40 caps for the Sevens side.
A product of Merchiston Castle School, Johnstone played his club rugby at capital based sides Currie and Watsonians before making his Edinburgh debut from the bench in the 2015/16 season opening victory over Leinster.
Johnstone scored his first try for Edinburgh in the 24-19 1872 Cup securing win over Glasgow, while the centre signed a new deal to keep him in the capital until 2020.
Home Shirt Sponsor: Firm of Messrs David Dalling
Date of birth: 17 April 1990
Edinburgh Debut: 4 September 2015 (Leinster)
Place of birth: Dumfries
Scotland 7s - 41 caps