[Transcriptomic dissection of low-light tolerance and regulatory mechanism of CsCOL2 in cucumber]

Cucumber is a light-demanding crop, and low-light stress readily induces shade avoidance syndrome (SAS), leading to yield reduction. To elucidate the molecular mechanisms underlying the shade avoidance response in cucumber under low-light conditions, In this study, transcriptome sequencing analysis for low-light tolerance was first performed in cucumber, and a downregulated gene CsCOL2 responding to low-light stress was identified. To clarify the role of CsCOL2 in the response to low-light stress and dissect its regulatory mechanism, we constructed overexpression and RNAi transgenic vectors of CsCOL2 and obtained the corresponding transgenic cucumber lines. The results demonstrated that knockdown of this gene promoted seedling morphogenesis and dry matter accumulation, and enhanced the tolerance of cucumber seedlings to low-light stress. However, overexpression of CsCOL2 aggravated oxidative damage and reduced chlorophyll content, conferring a low-light-sensitive and negative effect. Interestingly, exogenous melatonin could partially rescue this negative phenotype. This study reveals the critical regulatory role of CsCOL2 in low-light stress tolerance in cucumber, providing important genetic resources and novel research perspectives for breeding low-light-tolerant cucumber varieties.