| Summary: | 碩士 === 中國文化大學 === 生物科技研究所 === 94 === Recent studies show that seed storage protein deposit during maturation or degradation/mobilization during germination are likely associated with a novel group of cysteine proteases such as legumain-like asparaginyl endopeptidase (or named as vacuolar processing enzyme) and papaine-like cysteine protease. In our laboratory, similar legumain-like asparaginyl endopeptidase, SPAE, and papaine-like cysteine protease, SPCP2, have been isolated from sweet potato senescent leaves. Therefore, a putative role of SPAE and SPCP2 in sweet potato senescent leaves for bulk protein degradation and mobilization similar to the mechanism utilized in seed for storage protein degradation/mobilization during germination. In this research, the isolated, full-length cDNA of SPCP2 was constructed in recombinant pBI121 vector and transferred into Arabidopisis with Agrobacteria tumefaciens and floret dip transformation method. About 17 transgenic Arabidopsis plants were isolated that showed resistance to Kanamycin. Genomic PCR and RT-PCR analysis also demonstrated the existence and expression of SPCP2 in transgenic Arabidopsis plants. Morphological analysis showed that transgenic T1 plants exhibited higher incomplete capsule development percentage, lighter Fw and lower germination percentage of T1 and T2 seeds, and earlier flowering when compared to control plants. Based on these results, we conclude that a mechanism utilized for seed storage protein degradation/mobilization during germination may also be adopted by sweet potato senescent leaves, and senescent-associated gene, SPCP2, may slightly promote early flowering from vegetative phase transition to reproductive phase.
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