The effect of ethylene on squalene and β-sitosterol biosynthesis and its key gene network analysis in Torreya grandis nuts during post-ripening process

•Ethylene promote the post-ripening cracking of Torreya grandis nuts.•Ethylene enhanced the biosynthesis and accumulation of squalene.•TgHMGS, TgHMGR, and TgGGPS may play key roles in the accumulation of squalene.•Co-expression network identified key regulators of squalene and β-sitosterol biosynthesis.