MADS-box proteins contain a highly conserved DNA -binding domain at the N-terminus and function as transcription factors to regulate diverse processes, such as growth and development among others. The transcription factor can act as a homodimer or a heterodimer.

The zmm28 gene encodes a MIKC-type MADS-box transcriptional factor where the MADS (M) domain is followed by Intervening (I), Keratin-like (K), and C-terminal domains and belongs to the AP1-FUl clade of MADS-box genes. Constitutive expression of zmm28 resulted in greater height, increased yield, increased photosynthesis in leaves (higher expression of C4 photosynthetic genes), increased nitrogen assimilation (through improved nitrogenase reductase activity) and modulation of phytohormone (gibberellin and auxin) signalling.