The effect of arabinogalactan proteins on regeneration potential of juvenile citrus explants used for genetic transformation by Agrobacterium tumefaciens

A possible role of arabinogalactan proteins in control of shoot regeneration from stem explants of two citrus cultivars, Carrizo citrange and ‘Duncan’ grapefruit, was investigated. Treatment of explants with (β-d-Glc)₃ Yariv phenylglycoside, able to bind specifically to AGPs, led to a decrease of cumulative regeneration potential of both Carrizo citrange and ‘Duncan’ grapefruit. For Carrizo, lower cumulative regeneration potential on (β-d-Glc)₃ Yariv phenylglycoside-treated explants was the result of both lower number of shoots on the explants that had shoots (explant regeneration potential) and decreased percentage of explants with shoots. In the case of ‘Duncan’, treatment with (β-d-Glc)₃ Yariv phenylglycoside reduced cumulative regeneration potential only by lowering the percentage of explants with shoots, but it did not affect the number of shoots on the explants with shoots. Citrus explants treated with (α-d-Man)₃ Yariv phenylglycoside, which does not bind AGPs, responded similarly to untreated explants. Transformability of cells on the cut ends of explants was also lower for both cultivars following the treatment of explants with (β-d-Glc)₃ Yariv phenylglycoside. Our data suggest that arabinogalactan proteins play important role in processes controlling differentiation and genetic transformation of citrus cells by Agrobacterium.