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Functional Plant Biology Functional Plant Biology Society
Plant function and evolutionary biology
RESEARCH ARTICLE

Production and roles of IAA and ABA during development of superior and inferior rice grains

Heather M. Nonhebel https://orcid.org/0000-0001-9055-3095 A C and Karina Griffin https://orcid.org/0000-0002-6846-6494 A B
+ Author Affiliations
- Author Affiliations

A School of Science and Technology, University of New England, Armidale, NSW 2351, Australia.

B Present address: Macadamia Processing Company, 2 Cowlong Road, Lindendale NSW 2480, Australia.

C Corresponding author. Email: hnonheb2@une.edu.au

Functional Plant Biology 47(8) 716-726 https://doi.org/10.1071/FP19291
Submitted: 9 October 2019  Accepted: 10 February 2020   Published: 22 May 2020

Abstract

Current understanding of the role of plant hormones during cereal grain filling is confounded by contradictory reports on hormone production that is based on poor methodology. We report here on the accurate measurement of indole-3-acetic acid (IAA) and abscisic acid (ABA) by combined liquid chromatography-tandem mass spectrometry in multiple reaction-monitoring mode with heavy isotope labelled internal standards. ABA and IAA contents of superior versus inferior rice grains (ABA maxima 159 ng g–1 FW and 109 ng g–1 FW, IAA maxima 2 µg g–1 FW and 1.7 µg g–1 FW respectively) correlated with the expression of biosynthetic genes and with grain fill. Results confirm that grain ABA is produced primarily by OsNCED2(5), but suggest that ABA import and metabolism also play important roles in ABA regulation. The IAA content of grains is primarily influenced by OsYUC9 and OsYUC11. However, the distinct expression profile of OsYUC12 suggests a specific role for IAA produced by this enzyme. Co-expression of OsYUC12 with OsIAA29 indicates their involvement in a common signalling pathway. Co-expression and cis-element analysis identified several aleurone-specific transcriptional regulators as well as glutelin as strong candidates for detailed investigation for direct regulation by the auxin-signalling pathway.

Additional keywords: cereal grain fill, dorsal aleurone, endosperm, MRP-1, Oryza sativa, OsNF-YC, RISBZ1.


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