Studies on leaf senescence associated genes in Sweet Potato

• Main Authors: Huang, Yih-Jong, 黃義忠
• Other Authors: Chen, Shu-Chen
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/62697329601158754272

碩士 === 國立陽明大學 === 生物化學研究所 === 87 === Leaf senescence is the final stage of leaf development in higher plants. During this stage, senescing leaves recycle their movable nutrients to other parts of the plant. Nuclear genes are known to be involved in the senescence process, recent evidence indicates that leaf senescence is a form of programmed cell death (PCD). Molecular approaches have been recently employed to identify the senescence-associated genes (SAGs).In this thesis, two dimensional gel electrophoresis of proteins and mRNA differential display (DD-PCR) were used to study leaf senescence in sweet potato. By using two dimensional gel electrophoresis, four protein spots were identified to be leaf senescence-specific. They are named Sp30-1, Sp30-2, Sp43 and Sp45 according to the molecular mass estimated on the SDS-PAGE gel. After N-terminal sequencing and database comparison, Sp30-1 and Sp30-2 were found to be members of the cathepsin protein. The identities of Sp43 and Sp45 remain unknown, possibly due to N-terminal blocking. Utilizing DD-PCR method with 3 anchor primers and 12 H-AP primers, 16 differential-displayed cDNA fragments were obtained. These 16 cDNA fragments were first screened with reverse Northern hybridization, and 10 positive cDNA fragments were subjected to cloning. Three cDNA clones including pC20b, pG16-1 and pA15e were confirmed to be senescence-specific by Northern hybridization. pC20b was found to belong to cathepsin B subfamily. Further analysis showed that Sp30-1, Sp30-2 and pC20b are different cathepsin proteins. pG16-1 was found to be a receptor-like serine/threonine protein kinase. pA15e has no homologous gene sequence reported in the GenBank.