Endophytic Biostimulant Pyrroloquinoline Quinone Enhances Banana Growth and Primes Immunity Against <scp> <i>Fusarium</i> </scp> Wilt

Pyrroloquinoline quinone (PQQ) is a redox cofactor derived from prokaryotes that participates in various biological processes involving dehydrogenase enzymes. Previous field trials identified a PQQ-producing endophyte, Burkholderia seminalis 869T2, which enhances banana growth and reduces Fusarium wilt incidence from 24.5% to 3.4%. While more recent studies have confirmed its agricultural benefits across multiple plant species, the underlying molecular mechanisms remain unclear. Here, integrated omics and imaging mass spectrometry were employed to investigate the role of PQQ in planta. Our results indicate that PQQ achieves these outcomes by modulating key aspects of plant energy metabolism, including the tricarboxylic acid (TCA) cycle, oxidative phosphorylation, and NAD/NADP pathways. In addition, PQQ appears to influence phytohormone signalling pathways and trigger systemic plant resistance. Consistent with these molecular responses, exogenous PQQ enhanced root and shoot development and improved resistance to Fusarium infection. Collectively, these findings indicate that the endophyte functions as a biostimulant through PQQ production, coordinating plant metabolism and defence to counter pathogen invasion. This study provides mechanistic insight into plant-endophyte mutualism and highlights the potential of both PQQ and PQQ-producing endophytes as biostimulants for sustainable agricultural applications.