ABA 8'-Hydroxylase Mutations for Cereal Seed Dormancy Control
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Solution Overview
Problem
Current technologies lack a clear relationship between ABA content in cereal grains and dormancy, and there is a need for cereals with modified dormancy traits, particularly in barley and wheat, to prevent pre-harvest sprouting and ensure uniform germination.
Innovation Solution
Introduction of genetic variations in wheat plants that modify ABA 8'-hydroxylase activity by combining mutations in ABA 8'-hydroxylase-1 genes, leading to decreased ABA 8'-hydroxylase activity in the embryo, endosperm, or seed, which alters germination rates and dormancy levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ABA biosynthesis is increased through NCED overexpression, then seed dormancy is enhanced, but germination rate decreases
Solution Approach 1:
The patent changes the biochemical parameter by introducing a mutation in the NCED gene that alters substrate specificity. The mutated NCED enzyme prefers 9-cis-violaxanthin over 9-cis-zeaxanthin, changing the ABA biosynthesis pathway efficiency and timing. This parameter change allows enhanced dormancy through modified ABA accumulation kinetics without completely suppressing germination, as the enzyme activity is redirected rather than simply increased.
2Reliability
If ABA content is increased in mature seeds, then dormancy is promoted, but uniform germination is compromised
Solution Approach 1:
The patent introduces dynamic control of ABA biosynthesis through the mutated NCED enzyme that exhibits time-dependent substrate preference. During seed development, the enzyme accumulates ABA to establish dormancy, but during germination, the enzyme's activity pattern changes, allowing ABA levels to decline appropriately. This dynamic behavior ensures both adequate dormancy establishment and uniform germination when conditions are favorable.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The modified wheat plants exhibit altered germination rates and dormancy traits, with less than 90% of grains germinating within seven days, effectively addressing issues of pre-harvest sprouting and uniform germination.
Implementation Method 1
One pathway is the hydroxylation of ABA at the 8'-position to produce 8'-hydroxy ABA, which spontaneously isomerizes to phaseic acid (PA)
Implementation Method 2
8'-hydroxy ABA, which spontaneously isomerizes to phaseic acid (PA)
Data Source
Figure 1
Figure 2A~2D
Figure 3A~3F
AI summary
The present invention relates to polypeptides, and polynucleotides encoding therefor, which influence seed dormancy in cereals such as wheat and barley. In particular, the present invention relates to polypeptides with ABA 8'-hydroxylase activity, and polynucleotides encoding these proteins. Also provided are cereal plants which produce seeds that have altered rates of germination, and/or levels of dormancy, when compared to seeds from wild-type plants, as well as methods of producing such plants.