Fig. 4.

Expression and localization of MtDELLA1 in M. truncatula roots and AM phenotype of della1/della2 expressing della1-Δ18 driven by a vascular tissue-specific promoter. (A and B) Localization of MtDELLA1 promoter activity in noncolonized roots (−AMF) (A) and in roots colonized by G. versiforme (+AMF) (B). GUS-stained roots expressing pMtDELLA1:UidA indicate promoter activity in the vascular tissue and endodermis. Arrowheads mark cells containing arbuscules. Stars mark fungal hyphae. (C and D) Roots expressing pMtDELLA1:GFP-della1-Δ18 show consistent GFP signals in the nuclei of cells of the vascular tissue and endodermis; weaker signals are seen in some, but not all, cortical cells. Note that in this image the vascular tissue is not entirely in the focal plane (see also Fig. S6D). (E and F) Laser-scanning confocal microscope images of G. versiforme in roots of the della1/della2 mutant transformed with a control construct (E) or pMtPT9:della1-Δ18 (F). Expression of pMtPT9:della1-Δ18 restores arbuscule formation. (Scale bars: 100 µm in A and B; 250 µm in C–F.)