Programmed cell death: A mechanism for the lysigenous formation of secretory cavities in leaves of Dictamnus dasycarpus

• Published in: Plant science (Limerick) Vol. 225; pp. 147 - 160
• Main Authors: Zhou, Ya-Fu, Mao, Shao-Li, Li, Si-Feng, Ni, Xi-Lu, Li, Bin, Liu, Wen-Zhe
• Format: Journal Article
• Language: English
• Published: Ireland Elsevier Ireland Ltd 01.08.2014
• Subjects: 4',6-diamidino-2-phenylindole; Apoptosis; Cell Differentiation; Cell Nucleus; Cell Wall; cell walls; chromatin; Dictamnus - genetics; Dictamnus dasycarpus; DNA Cleavage; DNA damage; DNA Fragmentation; DNA, Plant; Essential oils; Formation; gel electrophoresis; leaves; Mitochondria; oils; Oils, Volatile - metabolism; Plant Cells; Plant Leaves; Plastids; Programmed cell death (PCD); Rutaceae; Secretory cavities; Vacuoles; PCD; TE; TUNEL; Secretory cavities; Essential oils; Rutaceae; DAPI; Dictamnus dasycarpus; TEM; Formation; Programmed cell death (PCD)
• ISSN: 0168-9452; 1873-2259; 1873-2259
• DOI: 10.1016/j.plantsci.2014.06.007

•One cell initiation and lysigenous oil cavities may be common in Dictamnus.•Lysigenous formation of the secretory cavities in D. dasycarpus is a PCD process.•Clusters of cells from a protoepidermal cell undergo different cell death fates.•Degradation products in the oil cavities may be used for the synthesis of essential oils.•A new description for different types of secretory cavities is determined. The formation of secretory cavities in Rutaceae has been the subject of great interest. In this study, cytological events that are involved in the lysigenous formation of the secretory cavities in the leaves of Dictamnus dasycarpus are characterized by an interesting pattern of programmed cell death (PCD). During the developmental process, clusters of cells from a single protoepidermal cell embark on different trajectories and undergo different cell death fates: the cell walls of the secretory cells have characteristics of thinning or complete breakdown, while the sheath cells present a predominantly thick-walled feature. A DAPI assay shows deformed nuclei that are further confirmed to be TUNEL-positive. Gel electrophoresis indicates that DNA cleavage is random and does not result in ladder-like DNA fragmentation. Ultrastructurally, several remarkable features of PCD have been determined, such as misshapen nuclei with condensed chromatin and a significantly diffused membrane, degenerated mitochondria and plastids with disturbed membrane systems, multivesicular bodies, plastolysomes, vacuole disruption and lysis of the center secretory cell. Cytological evidence and Nile red stains exhibit abundant essential oils accumulated in degenerated outer secretory cells after the dissolution of the center secretory cell. In addition, explanations of taxonomic importance and the relationship between PCD and oil droplet accumulation in the secretory cavities are also discussed.