A molecular module with PheIAA17 as the core significantly promotes lateral root germination

Monocot root systems comprise a large number of lateral roots to allow them to survive and colonize land. Auxin signaling pathways centered on Aux/IAA play a crucial role in lateral root development. However, in non-model monocot plants, the effects of Aux/IAA on lateral root initiation and number remain largely unknown. The present study transformed PheIAA17, a member of the Aux/IAA family of Moso bamboo, into rice and found that it significantly drove plants to produce lateral roots and improved the rooting rate. Quantitative experiments showed that PheIAA17 overexpression significantly affected the expression of ARF family members. Phylogenetic and promoter analyses indicate that PheARF3-2 belongs to class B ARF, and the promoter region contains auxin response elements. The results of yeast one-hybrid and dual-luciferase reporter assays confirmed that PheIAA17 bound specific fragments of the PheARF3-2 promoter to repress its transcriptional activity. Y2H and BiFC assay have shown that PheIAA17 and PheIAA30-3 could physically interact in vitro and in vivo. Taken together, this study reports a new molecular module centered on PheIAA17, which directs plants to alter root morphology through an increase in lateral roots.