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

RAINERI, JESICA; CARABALLO, LUCIANO NICOLÁS; GÓMEZ, MAXIMILIANO; CHAN, RAQUEL LÍA

Biomolecules

MDPI

Lugar: Basel; Año: 2023 vol. 13

The ideal rice phenotype is that of plants exhibiting fewer panicles with high biomass, largegrain number, flag leaf area with small insertion angles, and an erected morphology improving lightinterception. The sunflower transcription factor HaHB11, homeodomain–leucine zipper I, confersincreased seed yield and abiotic stress tolerance to Arabidopsis and maize. Here, we report theobtaining and characterization of rice plants expressing HaHB11 driven by its promoter or the 35Sconstitutive 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 wildtype. The former had an erected architecture, enhanced vegetative leaf biomass, rolled flag leaveswith a larger surface, sharper insertion angles insensitive to brassinosteroids, and higher harvestindex and seed biomass than the wild type. The combination of the distinct features exhibited byp35S: 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.