Abstract：Plant auxin receptor is the key point in auxin signaling pathways. We had cloned the auxin receptor homologous genes in cucumber (Cucumis sativus) in the previous work with the name of auxin signaling F box protein (CsAFB) and transport inhibitor response(CsTIR). In order to verify and further explore their function, we transformed them into both TIR1 loss-of-function mutant tir1-1 and wild-type Col-0 Arabidopsis thaliana and obtained homozygous transgenic plants, respectively. With the transformation of CsAFB and CsTIR into tir1-1 mutant, the abnormal phenotypes of root system development, exogenous auxin sensitivity and cell elongation response in tir1-1 could be rescued. Overexpression of CsAFB/CsTIR in wild-type A. thaliana, especially CsTIR, led to inhibited elongation of primary root, increased numbers of lateral roots, curled cotyledons, upward petioles, bending leaf margins towards abaxial surface and had obvious apical dominance. This work illustrated that CsAFB/TIR functioned similarly as AtTIR1 in Arabidopsis. These genes were probably auxin receptor homologous genes in cucumber. Overexpression of CsAFB/TIR could enhance the number of auxin receptors, amplify auxin signal and regulate plant growth and development in A. thaliana. This work will contribute to the further study of CsAFB/TIR functions and regulation mechanisms in cucumber.
