Fig. 4. Genetic engineering enables optogenetic control of shape change.

(A) Schematic of a light sensitive yeast two-hybrid. Blue light induces expression of HIS3 and lacZ reporters by inducing conformational changes in CRY2 to favor interaction with CIB1. Reporter genes are transcribed by recruitment of the Gal4 activation domain (AD). (B) β-Galactosidase assays of an auxotrophic strain lacking CIB1 (negative control), a strain not auxotrophic for l-histidine in the dark (positive control), and the auxotrophic strain depicted in (A) (experimental). (C) Schematic of a living composite irradiated with blue light in growth medium lacking l-histidine. (D) Volume change of living composites with experimental yeast irradiated with blue light or kept in the dark. Scale bar, 5 mm. (E) Volume change of living composites with each yeast strain when exposed to blue light or kept in the dark. (F) Patterned photoresponsive living composite with the experimental yeast strain in medium lacking l-histidine where blue light is first targeted on the left side and then the right side. Scale bar, 10 mm. Each data point represents the mean (n = 3), and error bars represent SD.