Gene expression of aleurone beta-amylase in rice
Date Issued
2006
Date
2006
Author(s)
Chen, Mei-Chen
DOI
zh-TW
Abstract
During the post-germination period, degradation of storage starch in cereals is critical to the viability of seedlings. Cereal β-amylases are important enzymes responsible for the mobilization of starch in germinating grains. In rice, β-amylase is synthesized de novo upon seed germination and is almost absent in dry seeds. However, detailed analyses on β-amylase expression in other tissues have not yet been performed. L10346 is a gene located in chromosome 7 which encodes the major β-amylase in germinating seeds. Analysis of the L10346 peptide sequence indicated that it is highly similar to other β-amylase sequences, including rye, maize, barley, arabidopsis, soybean, wheat, alfalfa, white, cowpea, sweet-potato (in the range of 72~88%). β-amylase activity was detected in the aleurone layers and scutella of 3-day germinating seeds. Polymorphism in rice amylases at early stage of seed germination was analyzed by zymogram. The temporal and spatial regulation of L10346 gene expression are presented by histochemical analysis of β-glucuronidase (GUS) activity in transgenic rice carrying L10346::gus fusion gene. GUS activity was detected in developing and germinating kernel. Subcellular localization study was performed by a fusion protein of β-amylase (L10346) and YFP. Fluorescence of YFP was present in both the cytosol and nucleus. Four major amylolytic enzymes were present in rice leaves and identified as β-amylase, namely BA1~4, based on the analysis of digestion products. The product of L10346 was assigned as the BA4. The decrease in BA4 activity was accompanied with the age gradient in rice leaves.
Subjects
β-澱粉水解酶
beta-amylase
Type
other