Utilizing MIKC-type MADS-box protein SOC1 for yield potential enhancement in maize

KEY MESSAGE: Overexpression of Zea mays SOC gene promotes flowering, reduces plant height, and leads to no reduction in grain production per plant, suggesting enhanced yield potential, at least, through increasing planting density. ABSTRACT: MIKC-type MADS-box gene SUPPRESSOR OF OVEREXPRESSION OF CONSTANS 1 (SOC1) is an integrator conserved in the plant flowering pathway. In this study, the maize SOC1 (ZmSOC1) gene was cloned and overexpressed in transgenic maize Hi-II genotype. The T(0) plants were backcrossed with nontransgenic inbred B73 to produce first generation backcross (BC(1)) seeds. Phenotyping of both transgenic and null segregant (NT) BC(1) plants was conducted in three independent experiments. The BC(1) transgenic plants showed new attributes such as increased vegetative growth, accelerated flowering time, reduced overall plant height, and increased grain weight. Second generation backcross (BC(2)) plants were evaluated in the field using two planting densities. Compared to BC(2) NT plants, BC(2) transgenic plants, were 12–18% shorter, flowered 5 days earlier, and showed no reduction in grain production per plant and an increase in fat, starch, and simple sugars in the grain. Transcriptome comparison in young leaves of 56-day-old BC(1) plants revealed that the overexpressed ZmSOC1 resulted in 107 differentially expressed genes. The upregulated transcription factor DNA BINDING WITH ONE FINGER 5.4 (DOF5.4) was among the genes responsible for the reduced plant height. Modulating expression of SOC1 opens a new and effective approach to promote flowering and reduce plant height, which may have potential to enhance crop yield and improve grain quality. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00299-021-02722-4.