Programmed Cell Death Involved In The Formation Of Traumatic Resin Ducts In Ailanthus Altissima

The formation of traumatic resin duct (TRD) was induced by mechanical wounding, ET and methyl jasmonate in the Secondary xylem of Ailanthus altissima. However, it was not clear that the programmed cell death was involved or not in the formation or the process of TRD’s formation. The purpose of this study was to show the distribution, the type of formation and cytological features of traumatic resin ducts with transmission electron microscopy technology, TUENL-DAPI assay and western blot technology, and to confirm traumatic resin ducts developmental processes was a programmed cell death (PCD) process and to explore the mechanism of ethylene and methyl jasmonate during the formation of traumatic resin ducts.The traumatic resin ducts of Ailanthus altissima were formed schizo-lysigenously, and the development encompassed at least three distinctive development stages:the stage of initial cells, the stage of inter-cellular space appearance and cavity enlargement, and the stage of mature ducts. The stage of initial cells:cells with larger volume, dense cytoplasm and clearly visible nucleus; the stage of inter-cellular space appearance and cavity enlargement:the number of epithelial cells and the secretory cavity increased significantly; the stage of mature ducts:there was only one layer of unlignificated epithelial cells around the cavity and the surrounding was the lignificated xylem cells.Transmission electron microscopy showed that the epithelial cell’s death was the typical characteristic PCD. Performing like the degradation of the cell wall, the agglutination of cytoplasm, organelles vesicles of vacuolar membrane fragmentation, degradation of nucleus. Combined with TUNEL assays, it was positive that nuclei DNA fragmentation in the late expansion of the cavities the decay of the epithelial cell was part of the apoptsis.These could prove the death of epithelial cells was a programmed cell death, and indicated that the programmed cell death involved in the process of traumatic resin ducts’ formation of Ailanthus altissima.Furthermore, from the observation of epitheliu’s electron microscopy, the synthetic place of resin was found in plastid and mitochondria. The resin was wrapped with vesicles, secreted by the cell membrane to the outside, entered into vacuole or dissolved directly in the cytoplasm.SDS-PAGE and western blot results showed that ethylene and methyl jasmonate could make caspase-3 like express, and the ethylene inhibitor 1-MCP could inhibit the expression of caspase-3 like.These were indicated that methyl jasmonate and ethylene were able to regulate the PCD by caspase-3 like.