Constitutive expression of the K-domain of a Vaccinium corymbosum SOC1-like (VcSOC1-K) MADS-box gene is sufficient to promote flowering in tobacco.

KEY MESSAGE: The K-domain of a blueberry-derived SOC1 -like gene promotes flowering in tobacco without negatively impacting yield, demonstrating potential for manipulation of flowering time in horticultural crops. ABSTRACT: The SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) and SOC1-likes, belonging to the MIKC(c) (type II) MADS-box gene subfamily, are major floral activators and integrators of plant flowering. Both MADS-domains and K (Keratin)-domains are highly conserved in MIKC(c)-type MADS proteins. While there are many reports on overexpression of intact MIKC(c)-type MADS-box genes, few studies have been conducted to investigate the effects of the K-domains. In this report, a 474-bp K-domain of Vaccinium SOC1-like (VcSOC1-K) was cloned from the cDNA library of the northern highbush blueberry (Vaccinium corymbosum L.). Functional analysis of the VcSOC1-K was conducted by ectopically expressing of 35S:VcSOC1-K in tobacco. Reverse transcription PCR confirmed expression of the VcSOC1-K in T0 plants. Phenotypically, T1 transgenic plants (10 T1 plants/event) flowered sooner after seeding, and were shorter with fewer leaves at the time of flowering, than nontransgenic plants; but seed pod production of transgenic plants was not significantly affected. These results demonstrate that overexpression of the K-domain of a MIKC(c)-type MADS-box gene alone is sufficient to promote early flowering and more importantly without affecting seed production.