Plant Senescence -Program cell death (PCD)- (biotic stress) (abiotic stress) - (initiation) (execution) -: cell

- 2 1. (senescence) 2. Hypersensitive response (HR) cell

-Senescence: cell

-HR: cell cell cell

Apoptosis PCD Chromatin condensesNuclear and plasma membrane Apoptotic bodies are formed and engulfed by phagocytes Narcosis of damaged cellsRupture of membrane Release of cellular contentsTissue inflammation

Autophagy in Bakers yeast-Autophagosomes engulf cytosol (+organelles) then taken into vacuole and hydrolyzed by hydrolytic enzymes.Plant cellYeast

PCD in cereal aleurone layer shows autophagy.

PCD processes in plant

Overview of Plant SenescenceSenescence is PCD process w/ terminal stage of development in both vegetative and reproductive organs. metabolism Arabidopsis thaliana

4-O-clock flower5-6 .13-14 . 1

metabolism metabolism

organells cell esp. plastids of mesophylls and parenchyma cells (pericarp)Chloroplasts of mesophyll cells gorontoplasts chromoplasts

YG=; MG1=; MG2=; S1, S2, S3= SAG = Senescence-associated gene

Pathway of chlorophyll degradation

chlorophyll carotenoids

carotenoids Isoprenoid pathway Lycopene

Pigment

Protein metabolism (photosynthesis)

Protein metabolism