Population genetics and phylogenetic analysis of the vrs1 nucleotide sequence in wild and cultivated barley

The Transcription Factor HaHB11 Boosts Grain Set and Yield in Rice Plants, Allowing Them to Approach Their Ideal Phenotype

The ideal rice phenotype is that of plants exhibiting fewer panicles with high biomass, large grain number, flag leaf area with small insertion angles, and an erected morphology improving light interception. The sunflower transcription factor HaHB11, homeodomain-leucine zipper I, confers increased seed yield and abiotic stress tolerance to Arabidopsis and maize. Here, we report the obtaining and characterization of rice plants expressing HaHB11 driven by its promoter or the 35S constitutive one. Transgenic p35S:HaHB11 plants closely resembled the ideal high-yield phenotype, whereas those carrying the pHaHB11:HaHB11 construct were hard to distinguish from the wild type. The former had an erected architecture, enhanced vegetative leaf biomass, rolled flag leaves with a larger surface, sharper insertion angles insensitive to brassinosteroids, and higher harvest index and seed biomass than the wild type. The combination of the distinct features exhibited by p35S:HaHB11 plants, including the increased number of set grains per panicle, supports the high-yield phenotype. We wondered where HaHB11 has to be expressed to achieve the high-yield phenotype and evaluated HaHB11 expression levels in all tissues. The results indicate that its expression is particularly necessary in the flag leaf and panicle to produce the ideal phenotype.

Functional analysis of the HD-Zip transcription factor genes Oshox12 and Oshox14 in rice

The homeodomain-leucine zipper (HD-Zip) transcription factor family plays vital roles in plant development and morphogenesis as well as responses to biotic and abiotic stresses. In barley, a recessive mutation in Vrs1 (HvHox1) changes two-rowed barley to six-rowed barley, which improves yield considerably. The Vrs1 gene encodes an HD-Zip subfamily I transcription factor. Phylogenetic analysis has shown that the rice HD-Zip I genes Oshox12 and Oshox14 are the closest homologues of Vrs1. Here, we show that Oshox12 and Oshox14 are ubiquitously expressed with higher levels in developing panicles. Trans-activation assays in yeast and rice protoplasts demonstrated that Oshox12 and Oshox14 can bind to a specific DNA sequence, AH1 (CAAT(A/T)ATTG), and activate reporter gene expression. Overexpression of Oshox12 and Oshox14 in rice resulted in reduced panicle length and a dwarf phenotype. In addition, Oshox14 overexpression lines showed a deficiency in panicle exsertion. Our findings suggest that Oshox12 and Oshox14 may be involved in the regulation of panicle development. This study provides a significant advancement in understanding the functions of HD-Zip transcription factors in rice.