Programmed Cell Death In Petal During Rose(Rosa×Hybrida) Flower Development

Programmed cell death (PCD) is an important part of the life cycle in plant.Flowers, the organs are responsible for sexual reproduction in plant, usuallyhave the shortest lifespan. Asensitive, tightly controlled program for cell deathmust exist during the flower development to regulate the flower lifespan. Rose,a kind of flowers that has important economic and aesthetic value, is widelyused in cut flower industry. In the present study, the purpose is to reveal themechanism of PCD during rose flower development in petal throughinvestigation of physiological, biochemical and molecular biology alteration inrose petals PCD. In this study, the rose petals were utilized for the experimental material.Development process of flower was divided into five stages that enable torepresent the entire developmental characteristic. In order to studysystematically the features of PCD, physiological and biochemical change aswell as biological molecular changes in petals during rose flowersdevelopment, the morphological and biochemical features, the structural andfunctional integrity of membrane, ethylene, genomic DNA and histones,proteins and proteinases including cysteine proteinase were determined. Wehope we can provide some theoretical evidences for the investigation in themechanism of PCD and extension of vase flower life-times. The results are as follows: 1. The fragmentation of genomic DNA (DNA laddering) was observed inagarose electrophoresis in the later stages (stage4, 5) of flower development inrose. The shrinkage of cytoplasm under light microscope and nucleicondensation stained by DAPI under fluorescence microscope were presentedin the later stages of development. Moreover, the more condensed both 3月季花发育过程中花瓣细胞程序化死亡机制研究cytoplasm and nuclei were presented at the later the developmental stage. Thecytoplasm shrinkage, nuclei condensation as well as DNA fragmentation arethe typical morphological and biochemical PCD features. 2. Membrane permeability in petals increased gradually during thedevelopment in rose, so did MAD. Simultaneously, the content of O2 -increased in the later developmental stages. All these alterations occurred inmembrane indicated that petal cell membrane occurred peroxidation, whichresulted in the loss of structural and functional integrity of membrane. Theincrease in ROS such as the O2 was mainly attributed to the reduction of -anti-oxidative enzymes activity such as SOD, POD and CAT during flowerdevelopment. 3. The soluble proteins in petals increased in early stages whereas decreasedin later stages during the flower development. This result suggested that theprotein biosynthesis was more dominant than the proteins degradation in theearly stages, however it reversed right in the later stages. Simultaneouslychromatin histones (H2) degradation took place in later stages, too. Aminoacid content in petals didn't increase correspondingly in the later stages. Thisindicated that the normal relationship between source and sink in nutrientstranslocation changed during flower development. 4.There was no detectable production in the early stages of flowerdevelopment in rose. Ethylene production started in stage 3 and increased withthe extension of developmental time. The production of ethylene wasconsistent to the appearance of PCD characteristics during flower development.Ethylene is likely to play a crucial role in promoting the petal PCD as asignaling during flower development in rose. ACC and ACC synthase activityalteration, which there were no detectable productions in early stages whileincreased in the later stages, appeared similar with that of ethylene duringflower development. Northern blot show that mRNA of ACC synthase geneaccumulated in the later stages and increased with the flower development.The change of mRNA level of ACC synthase gene was consistent to that of...