Expression of mutated SPL15m in sk156 results restores a WT phenotype and down regulates miR156b transcription. (A) Complementarity of miR156 with SPL15 sequences. Arrows show three cleavage sites (one used 10 out of 13 times) in SPL15 mRNA due to interaction with miR156b. SPL15m shows 11 nucleotides mutated in DNA sequence but unchanged in amino acid sequence. (B) SPL15 transcript levels in independent transgenic sk156 lines carrying 35S:SPL15m compared to WT (set at 1) and sk156. Error bars are standard deviations of the means. (C) and (D) Restoration of WT-like carotenoid levels in dry seeds of transgenic sk156 expressing SPL15m. Cryptoxanthin was undetectable in the mutant. (E) Restoration of WT-like plant growth in 35-d-old plants of sk156 expressing SPL15m. (F) Distinctive elongated leaf morphology of SPL15m-transformed plants compared to WT plants. (G) miR156b transcript levels in different transgenic sk156 lines expressing SPL15m compared to WT (set at 1) and sk156. A Duncan's multiple range test was conducted to separate significantly different means. Panels B, G, ± standard deviation; Panels C, D, ± standard error; p < 0.01 (**) and p < 0.05 (*).