The Cytokinins BAP and 2-iP Modulate Different Molecular Mechanisms on Shoot Proliferation and Root Development in Lemongrass ( Cymbopogon citratus ).

The known activities of cytokinins (CKs) are promoting shoot multiplication, root growth inhibition, and delaying senescence. 6-Benzylaminopurine (BAP) has been the most effective CK to induce shoot proliferation in cereal and grasses. Previously, we reported that in lemongrass ( Cymbopogon citratus ) micropropagation, BAP 10 µM induces high shoot proliferation, while the natural CK 6-(γ,γ-Dimethylallylamino)purine (2-iP) 10 µM shows less pronounced effects and developed rooting. To understand the molecular mechanisms involved, we perform a protein-protein interaction (PPI) network based on the genes of Brachypodium distachyon involved in shoot proliferation/repression, cell cycle, stem cell maintenance, auxin response factors, and CK signaling to analyze the molecular mechanisms in BAP versus 2-iP plants. A different pattern of gene expression was observed between BAP- versus 2-iP-treated plants. In shoots derived from BAP, we found upregulated genes that have already been demonstrated to be involved in de novo shoot proliferation development in several plant species; CK receptors (AHK3, ARR1) , stem cell maintenance (STM , REV and CLV3 ), cell cycle regulation ( CDKA-CYCD3 complex), as well as the auxin response factor ( ARF5 ) and CK metabolism ( CKX1 ). In contrast, in the 2-iP culture medium, there was an upregulation of genes involved in shoot repression ( BRC1 , MAX3 ), ARR4 , a type A-response regulator ( RR ), and auxin metabolism ( SHY2 ).