Abstract
Analysis of the functions of Short Vegetative Phase (SVP)-like MADS-box genes in barley (Hordeum vulgare) indicated a role in determining meristem identity. Three SVP-like genes are expressed in vegetative tissues of barley: Barley MADS1 (BM1), BM10, and Vegetative to Reproductive Transition gene 2. These genes are induced by cold but are repressed during floral development. Ectopic expression of BM1 inhibited spike development and caused floral reversion in barley, with florets at the base of the spike replaced by tillers. Head emergence was delayed in plants that ectopically express BM1, primarily by delayed development after the floral transition, but expression levels of the barley VRN1 gene (HvVRN1) were not affected. Ectopic expression of BM10 inhibited spike development and caused partial floral reversion, where florets at the base of the spike were replaced by inflorescence-like structures, but did not affect heading date. Floral reversion occurred more frequently when BM1 and BM10 ectopic expression lines were grown in short-day conditions. BM1 and BM10 also inhibited floral development and caused floral reversion when expressed in Arabidopsis (Arabidopsis thaliana). We conclude that SVP-like genes function to suppress floral meristem identity in winter cereals.
Highlights
Analysis of the functions of Short Vegetative Phase (SVP)-like MADS-box genes in barley (Hordeum vulgare) indicated a role in determining meristem identity
Three SVP-like genes were isolated from a barley cDNA library: Barley MADS1 (BM1; Schmitz et al, 2000), HvVRT2 (Kane et al, 2005), and a third gene, designated BM10
Expression levels of BM1, BM10, and HvVRT2 were monitored at weekly intervals in whole plants during the first 4 weeks of development
Summary
Analysis of the functions of Short Vegetative Phase (SVP)-like MADS-box genes in barley (Hordeum vulgare) indicated a role in determining meristem identity. Ectopic expression of BM10 inhibited spike development and caused partial floral reversion, where florets at the base of the spike were replaced by inflorescence-like structures, but did not affect heading date. AGL24 is expressed during vegetative development and is induced by treatments that accelerate floral transition, such as vernalization (prolonged exposure to low temperatures), long days, or the application of gibberellins (Yu et al, 2002; Michaels et al, 2003). These data suggest that AGL24 acts to promote floral transition in response to vernalization and long-day conditions (Yu et al, 2002; Michaels et al, 2003). In winter cereals, such as wheat (Triticum aestivum) and barley (Hordeum vulgare), the floral transition can be accelerated by long days or by prolonged cold treatment (vernalization) and is subject to genetic variation that affects the number of leaves that develop prior to the floral transition (Boyd et al, 2003)
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