Role of programmed cell death for seed filling
We elucidated that programmed cell death (PCD) in maternal seed parts is required for endosperm development and seed filling, thus contributing to the control of seed size in cereal grains. The distributions of TUNEL-positive nuclei, expression of PCD-related genes and cascades of caspase-like activities have revealed that each seed tissue follows an individual PCD pattern. Earlier we found that Triticeae-specific Jekyll gene, exclusively expressed in the nucellar projection, is involved in terminal differentiation of the nucellar tissues switching their cell fate to death (Radchuk et al., Plant Cell 2006). Further, we have established that tissue-specific genes encoding vacuolar processing enzyme (VPE) are required for PCD in distinct grain tissues. Using transcriptional and metabolic profiling, flow cytometry, 13C-feeding experiments, histology and nuclear magnetic resonance imaging of grains we demonstrated that PCD in pericarp is required to provide space for the expanding endosperm and embryo (Radchuk et al., New Phytology 2018). PCD in the nucellar projection contributes to nutrient flow towards endosperm and is controlled by expanded VPE2 subfamily in barley (Mascher et al., Nature 2017) and other Triticeae, compared to other Poaceae species. In current research, we elucidate the functional role of specific gene family members of VPE.