The Effect of a Floury Gene Floury7 (FLO7) in Rice (Oryza sativa L.) on Grain Composition and Starch Synthesis Related Genes

• Main Authors: Meng-Ying Lin, 林孟穎
• Other Authors: 林彥蓉
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/3gvjk2

碩士 === 國立臺灣大學 === 農藝學研究所 === 101 === Opaque rice endosperm including floury, glutinous, and dull grains is important for food and industrial applications. The corresponding mutants not only provide valuable genetic materials for elucidating metabolic processes related to nutrient storage during grain filling but also facilitate the understanding the gene network of starch synthesis related genes. A floury mutant, WY14, is one of the mutants from TK8 induced by EMS which possessed lower amylose content (14.20 ± 0.05%) compared to that of wild type TK8 (18.15 ± 0.58 %). WY14 proceeded worse grain filling and accumulated lower dry weight of grains in the first crop season of 2012 than TK8 did, but not in the second crop season of 2012. Profiles of total storage proteins in WY14 and TK8 revealed no difference. However, WY14 had higher amount of fatty acid and proportion of palmitic acid and arachidic acid than TK8, and WY14 possessed additional 0.16 % of long-chain saturated fatty acid, behenic acid. The mutated gene, conferring floury endosperm of WY14, was isolated by positional cloning, which was named FLO7 and annotated as ABC transporter. The mutation of FLO7 responsible for floury endosperm was confirmed by RNAi. T1 seeds of RNAi lines showed segregation of both translucent and floury endosperm. Identification of 4 FLO7 transcripts by 3’ RACE suggested that the main FLO7 transcript in endosperm is FLO7-2a. FLO7 expressed not only in vegetative tissues but also in immature caryopsis, and FLO7 expressed differently with significance between WY14 and TK8 at 15 DAP. Gene expression of most starch biosynthesis related enzymes acting in cytosol had higher level, but not those in amyloplast which were down-regulated in WY14 as compared to in TK8. Futhermore, higher expression of PPDKA and cyPPDKB may account for higher total amount of fatty acid in WY14 than in TK8. This research contributes to the relevant regulatory mechanism and genetic network related to starch synthesis in rice endosperm. The flo7 of WY14 may be applied to breed new floury varieties by marker assisted selection for multipurpose usage of rice grains.