Award details

Regulation and genetic manipulation of pre- and post-harvest sprouting in cereals

Reference	BBS/E/C/00804033
Principal Investigator / Supervisor	Dr John Lenton
Co-Investigators / Co-Supervisors
Institution	Rothamsted Research
Department	Rothamsted Research Department
Funding type	Research
Value (£)	89,163
Status	Completed
Type	Institute Project
Start date	01/04/1997
End date	31/03/1999
Duration	24 months

Abstract

Pre-harvest sprouting (PHS) is detrimental to both barley malting and wheat breadmaking quality. Grains that sprout prematurely whilst still in the ear may bypass the normal dormancy induction program or may exhibit weak dormancy thus requiring only a short period of afterripening. In either case, the normal germination program appears to be initiated prematurely. Gibberellin (GA) produced in the embryo diffuses to the aleurone and induces the synthesis of hydrolytic enzymes, including the main starch degrading enzyme, alpha- amylase. In a collaborative project with Pauls Malt, hormonal changes have been quantified in sound barley samples micromalted in the absence and presence of added GA3, which is known to hasten modification. In field-grown wheat, there are also situations in cool, moist seasons in which pre-maturity alpha-amylase may occur in the absence of visible embryo germination (ie. grains remain dormant). Whatever the cause, the presence of alpha- amylase activity in wheat flours used for breadmaking results in the production of dextrins that cause sticky crumb structure and block slicing machines. This project aims to define which alpha-amylase gene families contribute to PHS and prematurity alpha- amylase in wheat, in which tissues they are expressed, and how that expression is regulated. In addition to hormonal controls, there is some evidence for so- called sugar sensing whereby repression of certain amylase gene families occurs. Hormone- deficient mutants will be used to determine the extent of GA- responsiveness in diploid barley, whereas inhibitors of GA biosynthesis will be used in hexaploid breadwheat. Ultimately, transgenic wheat with down-regulated GA 20-oxidase will be generated. Other transformation targets include overexpression of Vp1 and direct suppression of alpha-amylase. Transcript abundances will be determined by RT-PCR or Northern blots, protein activity determined using a blocked maltoheptaoside substrate and isozyme patterns using IEF gels. Gibberellins (GAs) and abscisic acid (ABA) will be quantified by GC- MS. Objectives 1996 Compare pattern of alpha-amylase gene expression in developing grains with post- germinative mature wheat. Prepare and assess activity of alpha-amylase promoter-GUS fusion constructs in transient and stable wheat transformation systems. 1997 Compare hormonal status and amylase, Vp1 and GA 20-oxidase expression patterns in glasshouse-grown and wet- weather induced PHS in wheat. Develop gene- specific probes for the wheat GA 20- oxidase gene families and use them to determine expression patterns in scutella of germinating wheat. Continue characterisation of blocks in GA pathway of barley mutants.

Summary

unavailable

Committee	Closed Committee - Agri-food (AF)
Research Topics	X – not assigned to a current Research Topic
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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