The impact of the indica rice SSIIa allele on the apparent high amylose starch from rice grain with downregulated japonica SBEIIb

Document Type

Journal Article

Publication Title

Theoretical and Applied Genetics

Volume

133

Issue

1

Publisher

Springer

School

School of Science

RAS ID

35595

Funders

CSIRO Food Future National Research Flagship Chinese Scholarship Council Australian National University

Comments

Luo, J., Butardo Jr., V. M., Yang, Q., Konik-Rose, C., Colgrave, M. L., Millar, A., … Li, Z. (2020). The impact of the indica rice SSIIa allele on the apparent high amylose starch from rice grain with downregulated japonica SBEIIb. Theoretical and Applied Genetics, 133(10), 2961-2974. https://doi.org/10.1007/s00122-020-03649-2

Abstract

Rice (Oryza sativa) genotypes with inactive starch synthase IIa (SSIIa) with recessive variants of starch branching enzyme IIb (SBEIIb) exhibit a range of alterations in grain phenotype, starch granule morphology, starch granule bound proteins, starch structure, and functional properties. However, the interactions between the two enzymes have not been thoroughly investigated yet. We analysed recombinant rice lines having down-regulated SBEIIb expression (SBEIIbDR) with either indica or japonica type SSIIa (SSIIaind or SSIIajap). In SBEIIbDR rice starch granules, the increased abundance of two protein bands (SSI and SSIIa) was found with eight additional protein bands not generally associated with starch granules. The amount of SSIIa was higher in SSIIaindSBEIIbDR than SSIIajapSBEIIbDR, which indicated that indica type SSIIa, possibly in the monomer form, was extensively involved in starch biosynthesis in the SBEIIbDR endosperm. Furthermore, SSIIaindSBEIIbDR grains had higher total starch content and higher starch swelling power than SSIIajapSBEIIbDR lines, but the amylopectin gelatinization temperatures and enthalpy and the apparent amylose content remained similar. In summary, this work suggests that SSIIaind can partly compensate for the alteration of starch synthesis resulting from the SBEIIb down-regulation in japonica background without reducing its amylose content. The study provides insight into the starch structural and textural improvements of high amylose starch.

DOI

10.1007/s00122-020-03649-2

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Link to publisher version (DOI)

10.1007/s00122-020-03649-2