Fig. 5. Ubiquitous overexpression of MP and NPH4. (A) Hypocotyl length of seedlings of the indicated genotypes germinated and grown in the dark for 5 days in the presence of 20 µM IAA. Sample sizes are 15 to 82 seedlings. Columns represent the mean±s.d. Note that both 35S::NPH4 and 35S::MP restore auxin sensitivity. (B) Normalization of the vegetative leaf shape defects (nph4-103, left) by expression of 35S::NPH4 (center) and 35S::MP (right) in the nph4-103 background. (C) Vegetative and inflorescence phenotypes of wild-type, 35S::MP, 35S::NPH4 and 35S::NPH4; 35S::MP plants. Left column contains rosettes at 21 dag, represented by the insert in the bottom panel, because of the delayed development of 35S::NPH4; 35S::MP plants. Large rosette in this panel is at 35 dag and has bolted. Note the formation of extremely twisted leaves in 35S::NPH4; 35S::MP plants of all stages and the appearance of numerous small leaves late in vegetative development (white arrow in 35S::NPH4; 35S::MP rosette). Middle column indicates inflorescence tips at 40 dag. Inflorescences of 35S::NPH4 plants are indistinguishable from wild type, while inflorescences of 35S::MP plants produce distorted, usually sterile, flowers and may terminate in pin-shaped inflorescence tips (white arrow). Inflorescences of 35S::NPH4; 35S::MP plants do not produce any flowers. (Right column) Upper two images are scanning electron micrographs of pre-bolting inflorescence meristems. Note that there is no recognizable effect of 35S::NPH4 expression on meristem organization or size. (Lower two images) Post-bolting inflorescence meristems of 35S::NPH4; 35S::MP plants invariantly lack flower primordia, which are produced at variable density in the inflorescence meristems of 35S::MP plants (white arrows). Scale bars: 100 µm. (D) Synergistic phenotype effects associated with co-expression of NPH4 together with regions of the MP coding sequence, both under control of the CaMV 35S promoter. Synergistic effects are indistinguishable from the phenotype shown in the lower panel of C and were observed in all (yes) or none (no) of at least seven double overexpressing plants. Constructs refer to amino acid residues of the MP-coding sequence (Hardtke and Berleth, 1998): MP-289, residues 1-289; MP-785, residues 1-785; MP288+, residues 288-902.