Study of glyoxylate cycle regulation by sucrose during protocorm growth in Phalaenopsis aphrodite

摘要

The glyoxylate cycle plays a central role in converting storage oil to soluble carbohydrate in oilseeds to support growth during germination Enzyme activity or transcript accumulation of key enzymes of the glyoxylate cycle isocitrate lyase (ICL)/ malate synthase (MLS) are downregulated by carbon catabolite repression during seed germination Without endosperm and cotyledon orchid seeds was found large amount of lipid reserved in the immature embryo and carbohydrates play a vital role to support protocorm development during tissue culture To investigate the metabolism of orchid seed during germination I explored how the sucrose regulates the glyoxylate cycle during the Phalaenopsis aphrodite protocorm development We identified ICL and MLS from OrchidBase and named as PaICL and PaMLS Expression analysis showed that sucrose depressd the expression of both PaICL and PaMLS and the transcripts level of PaMLS was extremely downregulated by sucrose treatment For identification of putative genes encoded transcription factor which regulate expression of malate synthase digital expression analysis comparing transcriptomes derived from day 4 and day 7 protocorms cultured on 1/2 MS medium and sucrose was performed In addition 2-kb upstream sequence of malate synthase gene was retrieved from OrchidBase for analyzing regulatory motif by plantPAN Combining transcriptomic and regulatory motif analysis one putative positive (PaHB5) and seven negative transcription factor genes (PaANT PaMADS2 PaMYB4 PaPIF3 PaRAV1-1 PaWRKY18 PaWRKY71) are identified Dual luciferase assay was adopted to analyze binding ability of PaHB5 to the promoter of malate synthase gene Results show that PaHB5 could increase expression of malate synthase gene for 2 73 fold This is the first study reveal that the molecular mechanism underlying glyoxylate cycle

獎項日期	2014 9月 3
原文	English
監督員	Wen-Chieh Tsai (Supervisor)