Comparison of amylopectin structure and activities of key starch synthesis enzymes in the grains of rice single-segment substitution lines with different Wx alleles

Abstract

The Wx gene is the major gene controlling amylose synthesis in rice endosperm. So far, the Wx gene can be mainly classified into five common alleles, wx, Wx t , Wx g1 , Wx g2 , and Wx g3 , according to their amylose phenotypes. Besides, the Wx allelic variation was also found to play an important role in regulating other physicochemical properties of rice starch. However, the specific physiological and starch structural mechanisms are not clear yet. With a set of singlesegment substitution lines harboring five different Wx alleles, the genotype differences in amylopectin structure and dynamic changes of activities of key starch synthesis enzymes were investigated. The distinct Wx genotype difference in chain length distribution of amylopectin was confirmed by size exclusion chromatography. There were clear allelic differences in activities of starch synthesis enzymes during grain filling. The Wx allelic variation had the highest impact on the activities of starch branching enzyme, followed by pullulanase, and soluble starch synthase, while no influence on isoamylase activity. Differences in structural features of amylopectin and mean enzyme activities during grain filling period correlated well with most of the variations in starch property traits. These findings indicate that the Wx allelic variation may affect starch structure and physicochemical properties through selectively influencing activities of starch synthesis enzymes in developing rice grains. The present results will contribute to our understanding of the regulation of starch biosynthesis in rice endosperm.

Crystalline, thermal and swelling properties of starches from single‐segment substitution lines with different Wx alleles in rice (Oryza sativa L.)

“…The reason that the Wx g1 and Wx g2 genotype starches showed similar RC values may be attributed to their differences in amylopectin structure. Compared with the Wx g1 genotype starch, the Wx g2 starch was found to have a higher proportion of medium‐length chains (degree of polymerization, 28–67) in amylopectin, which may have the ability to form more stable double helices and therefore compensate for the reduction in RC caused by the AAC variation.…”

Enhancing menaquinone-7 production in recombinant Bacillus amyloliquefaciens by metabolic pathway engineering

“…However, previous research reported that gene allelic variation will affect the activity of the corresponding enzyme. 29,30 In order to investigate whether these amino acid variations will lead to a difference in enzyme activity, the recombinant plasmids with the above genes from strain Y-2 or W-21 were constructed, and electro-transformed into B. subtilis 168 competent cells. Consistent with the expected molecular mass of the corresponding enzyme, the thick protein band that appeared when SDS-PAGE was performed was observed in the cell-free extracts from strains carrying the recombinant plasmid (data not shown).…”

Effect of calcium and magnesium on starch synthesis in maize kernels and its physiological driving mechanism

“…The rest of the homogenate was centrifuged at 10,000 g for 15 min, and the supernatant was used for the determination of SS, ADPG, SBE, and DBE activities ( Dai, 2010 ). UDPG and SSS were determined according to the method of ( Teng et al., 2015 ). All parameters were measured four times.…”