Journal
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
Volume 116, Issue 11, Pages 5182-5187Publisher
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1815465116
Keywords
floret fertility; grain number; duplication; HD-Zip vertical bar transcription factor; wheat
Categories
Funding
- Genomics for Agricultural Innovation Program of the Ministry of Agriculture, Forestry, and Fisheries of Japan [TRS1002]
- Japan Society for the Promotion of Science (JSPS) [16K18635]
- Israel Ministry of Agriculture and Rural Development [20-10-0066]
- US Agency for International Development Middle East Research and Cooperation [M34-037]
- German Research Foundation [BL462/10]
- HEISENBERG Program of the German Research Foundation (DFG) [SCHN 768/8-1]
- IPK core budget
- Grants-in-Aid for Scientific Research [16K18635] Funding Source: KAKEN
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Floret fertility is a key determinant of the number of grains per inflorescence in cereals. During the evolution of wheat (Triticum sp.), floret fertility has increased, such that current bread wheat (Triticum aestivum) cultivars set three to five grains per spikelet. However, little is known regarding the genetic basis of floret fertility. The locus Grain Number Increase 1 (GNI1) is shown here to be an important contributor to floret fertility. GNI1 evolved in the Triticeae through gene duplication. The gene, which encodes a homeodomain leucine zipper class I (HD-Zip I) transcription factor, was expressed most abundantly in the most apical floret primordia and in parts of the rachilla, suggesting that it acts to inhibit rachilla growth and development. The level of GNI1 expression has decreased over the course of wheat evolution under domestication, leading to the production of spikes bearing more fertile florets and setting more grains per spikelet. Genetic analysis has revealed that the reduced-function allele GNI-A1 contributes to the increased number of fertile florets per spikelet. The RNAi-based knockdown of GNI1 led to an increase in the number of both fertile florets and grains in hexaploid wheat. Mutants carrying an impaired GNI-A1 allele out-yielded WT allele carriers under field conditions. The data show that gene duplication generated evolutionary novelty affecting floret fertility while mutations favoring increased grain production have been under selection during wheat evolution under domestication.
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