Epsilon Archive for Student Projects

Abstract

Jojoba (Simmondsia chinensis) is a unique desert shrub that accumulates wax esters (WEs) instead of triacylglycerols (TAGs) as the primary seed storage lipid. While WEs are valued for industrial applications, their degradation during seed germination remains poorly understood, limiting the development of high WE-yielding transgenic crops. This study aimed to identify and functionally characterize key genes involved in WE hydrolysis during germination.

Transcriptomic analysis was performed on cotyledon and hypocotyl tissues at 1, 15, and 35 days after germination (DAG). Differential expression gene (DEG) analysis revealed distinct transcriptional patterns between the two tissues, with peak DEGs abundance between 1 and 15 DAG, suggesting early activation of tissue-specific lipid mobilisation. A GDSL esterase/lipase candidate (Sc04g0004020, WEH1) was selected for further validation.

A transient expression system was established in Nicotiana benthamiana leaves, where WE and TAG synthetic pathways were reconstructed. In two independent experiments, WEH1 expression led to a reduction in WE content without affecting TAG levels, indicating substrate specificity. This reduction, while not statistically significant, suggested a role for WEH1 in WE hydrolysis. Such insignificance was likely due to complex regulatory mechanisms of WEH1 expression and incomplete enzymatic activation.

This work provides transcriptomic and functional evidence for a jojoba WE hydrolase candidate, offering new insights into lipid degradation during germination. These findings lay the groundwork for engineering oilseed crops with improved WE traits and robust germination performance.