Proefschrift
Coming of age: An insight into the mechanisms of developmental ageing and post-harvest senescence in lettuce
The vegetative growth period for leafy vegetables like lettuce is essential for yield and quality.
- Auteur
- J. van Lieshout
- Datum
- 25 februari 2026
- Links
- Thesis in Leiden Repository
During this period the plant undergoes several phase transitions, like vegetative phase change (VPC) and heading, but also age-dependent deterioration called senescence. We investigate both phenotypic and transcriptional changes in lettuce leaf tissue that show the shift to an adult phase. We show that this shift is associated with several morphological changes, as well as decreasing miR156 and increasing SPL gene expression. A short-tandem mimic of miR156 (STTM156) exhibits reduced miR156 and increased SPL expression, resulting in earlier VPC, but also heading and flowering. Additionally, we show that heading coincides with increased cell proliferation at the abaxial side. Through auxin transport inhibition experiments and transcriptome analysis, we hypothesise that this is a result of asymmetric polar auxin transport. Finally, we mapped the natural variation in pre- and post-harvest senescence of lettuce grown in the field and in controlled conditions. Using a developed screening method for chlorophyll, we identified a number of genetic loci related to leaf senescence, but also oxidative colouration. This research helps us understand what mechanisms drive ageing in lettuce, which can be used for future breeding purposes.