Heterologous expression of ZmWBC33 in Arabidopsis thaliana to assess its putative involvement in strigolactone transport

ZmWBC33 is a member of the maize (Zea mays L.) ABCG transporter family. ZmWBC33 was firstly identified from RNA-seq data in maize root, showing a strong induction of transcription in response to nitrate starvation and gene expression localization patterns similar to those observed for a strigolactone (SL) transporter in petunia. To functionally characterize this protein, heterologous expression of the maize ZmWBC33 in Arabidopsis thaliana was performed. Four lines carrying ZmWBC33 were obtained, two with and two without the integration of the green fluorescent protein (GFP). The GFP signal was localised at the plasma membrane of epidermal cells both in leaves and roots, consistent with a putative role of ZmWBC33 as a transporter. Furthermore, a hydroponic growth system was developed and the Phelipanche ramosa germination bioassay was utilized to indirectly measure the SL contents in root exudates obtained from both control and ZmWBC33-expressing plants in different nutritional conditions. Our results provide preliminary information on the putative functions of ZmWBC33.