The Genetic Basis of Composite Spike Form in Barley and 'Miracle-Wheat'.

Abstract

Inflorescences of the tribe Triticeae, which includes wheat (Triticum sp. L.) and barley (Hordeum vulgare L.) are characterized by sessile spikelets directly borne on the main axis, thus forming a branchless spike. 'Compositum-Barley' and tetraploid 'Miracle-Wheat' (T. turgidum convar. compositum (L.f.) Filat.) display noncanonical spike-branching in which spikelets are replaced by lateral branch-like structures resembling small-sized secondary spikes. As a result of this branch formation 'Miracle-Wheat' produces significantly more grains per spike, leading to higher spike yield. In this study, we first isolated the gene underlying spike-branching in 'Compositum-Barley,' i.e., compositum 2 (com2). Moreover, we found that COM2 is orthologous to the branched head(t) (bh(t)) locus regulating spike branching in tetraploid 'Miracle-Wheat.' Both genes possess orthologs with similar functions in maize BRANCHED SILKLESS 1 (BD1) and rice FRIZZY PANICLE/BRANCHED FLORETLESS 1 (FZP/BFL1) encoding AP2/ERF transcription factors. Sequence analysis of the bh(t) locus in a collection of mutant and wild-type tetraploid wheat accessions revealed that a single amino acid substitution in the DNA-binding domain gave rise to the domestication of 'Miracle-Wheat.' mRNA in situ hybridization, microarray experiments, and independent qRT-PCR validation analyses revealed that the branch repression pathway in barley is governed through the spike architecture gene Six-rowed spike 4 regulating COM2 expression, while HvIDS1 (barley ortholog of maize INDETERMINATE SPIKELET 1) is a putative downstream target of COM2. These findings presented here provide new insights into the genetic basis of spike architecture in Triticeae, and have disclosed new targets for genetic manipulations aiming at boosting wheat's yield potential.

• Authors: Naser Poursarebani, Tina Seidensticker, Ravi Koppolu, Corinna Trautewig, Piotr Gawroński, Federica Bini, Geetha Govind, Twan Rutten, Shun Sakuma, Akemi Tagiri, Gizaw M Wolde, Helmy M Youssef, Abdulhamit Battal, Stefano Ciannamea, Tiziana Fusca, Thomas Nussbaumer, Carlo Pozzi, Andreas Börner, Udda Lundqvist, Takao Komatsuda, Silvio Salvi, Roberto Tuberosa, Cristobal Uauy, Nese Sreenivasulu, Laura Rossini, Thorsten Schnurbusch
• Journal: Genetics (Genetics) Vol. 201 Issue 1 Pg. 155-65 (Sep 2015) ISSN: 1943-2631 [Electronic] United States
• PMID: 26156223 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
• Copyright: Copyright © 2015 by the Genetics Society of America.

Chemical References

• Plant Proteins
• Transcription Factors

Topics

• Chromosome Mapping
• Chromosomes, Plant
• Gene Expression Profiling
• Gene Expression Regulation, Plant
• Hordeum (genetics, ultrastructure)
• Plant Proteins (genetics)
• Sequence Homology, Nucleic Acid
• Transcription Factors (genetics)
• Triticum (genetics, ultrastructure)