Improving seed size, seed weight and seedling emergence inCamelina sativaby overexpressing theAtsob3-6gene variant

Seedling stand establishment is a critical factor affecting crop yield in low-precipitation agricultural regions. This is especially true for small seeded crops, such asCamelina(Camelina sativa) and canola (Brassica napus), that need to be planted shallow. Deeper planting would be desirable so that seeds can access soil moisture and bigger seeds could improve emergence and stand establishment by providing the energy necessary for seedling elongation.AHL(AT-Hook Containing, NuclearLocalized) genes play an important role in seedling growth and development. AHL proteins contain two structural units, the DNA-binding AT-hook motif and thePlant andProkaryoteConserved (PPC) domain, required for protein-protein interactions. Our previous studies demonstrate thatAtAHL29/SOB3(Suppressorof phytochromeB-4 #3) regulates seedling development inArabidopsis(Arabidopsis thaliana). Activation-tagged overexpression ofAtSOB3(Atsob3-D) represses the long-hypocotyl phenotype of anArabidopsisphytochrome B mutant. In contrast, overexpression of theAtsob3-6variant (Atsob3-6-OX), with a non-functional AT-hook, confers a long-hypocotyl phenotype. In this study, we demonstrate the role ofAtsob3-DandAtsob3-6-OXin modulating seed size and hypocotyl length in the brassicasArabidopsisandCamelina. InArabidopsis,Atsob3-Dreduces seed weight whereasAtsob3-6-OXincreases seed weight and size when compared to the wild type. Similarly,Atsob3-6-OXtransgenicCamelinaseedlings are taller than the wild type, and produce larger and heavier seeds. These largerAtsob3-6-OX Camelinaseeds also confer better emergence in deep-soil planting when compared to the wild type. Taken together,Atsob3-6-OXincreases seed size, seed weight, seedling hypocotyl length and stand establishment in the oilseed cropCamelina.