Divergence of expression pattern contributed to neofunctionalization of duplicated HD‐Zip I transcription factor in barley. Issue 3 (7th January 2013)

• Record Type: Journal Article
• Authors: Sakuma, Shun; Pourkheirandish, Mohammad; Hensel, Goetz; Kumlehn, Jochen; Stein, Nils; Tagiri, Akemi; Yamaji, Naoki; Ma, Jian Feng; Sassa, Hidenori; Koba, Takato; Komatsuda, Takao
• Is Part Of: New phytologist. Volume 197:Issue 3(2013)
• Page Start: 939
• Page End: 948
• Publication Date: 2013-01-07
• Subjects: Botany -- Periodicals; 580
• DOI: 10.1111/nph.12068
• Languages: English
• ISSNs: 0028-646X

Abstract

<abstract abstract-type="main" id="nph12068-abs-0001"> <title>Summary</title> <p> <list id="nph12068-list-0001" list-type="bullet"> <list-item> <p>Barley (<italic>Hordeum vulgare</italic>) spikes are developmentally switched from two‐rowed to six‐rowed by a single recessive gene, <italic>six‐rowed spike 1</italic> (<italic>vrs1</italic>), which encodes a homeodomain‐leucine zipper I class transcription factor. <italic>Vrs1</italic> is a paralog of <italic>HvHox2</italic> and both were generated by duplication of an ancestral gene. <italic>HvHox2</italic> is conserved among cereals, whereas <italic>Vrs1</italic> acquired its current function during the evolution of barley. It was unclear whether divergence of expression pattern or protein function accounted for the functionalization of <italic>Vrs1</italic>.</p> </list-item> <list-item> <p>Here, we conducted a comparative analysis of protein functions and gene expression between <italic>HvHox2</italic> and <italic>Vrs1</italic> to clarify the functionalization mechanism.</p> </list-item> <list-item> <p>We revealed that the transcriptional activation activity of HvHOX2 and VRS1 was conserved. <italic>In situ</italic> hybridization analysis showed that <italic>HvHox2</italic> is localized in vascular bundles in developing spikes, whereas <italic>Vrs1</italic> is expressed exclusively in the pistil, lemma, palea and lodicule of lateral spikelets. The transcript abundance of <italic>Vrs1</italic> was > 10‐fold greater than that of <italic>HvHox2</italic> during the pistil developmental stage, suggesting that the essential function of <italic>Vrs1</italic> is to inhibit gynoecial development. We demonstrated the quantitative function of <italic>Vrs1</italic> using RNAi transgenic plants and <italic>Vrs1</italic> expression variants. Expression analysis of six‐rowed spike mutants that are nonallelic to <italic>vrs1</italic> showed that <italic>Vrs1</italic> expression was up‐regulated by <italic>Vrs4</italic>, whereas <italic>HvHox2</italic> expression was not.</p> </list-item> <list-item> <p>These data demonstrate that the divergence of gene expression pattern contributed to the neofunctionalization of <italic>Vrs1</italic>.</p> </list-item> </list> </p> </abstract>