(A) Morphological events in Stentor regeneration. At t=0,the membranellar band is shed during sucrose shock. The body cilia remain on the cell. After sucrose shock the frontal field protrudes, resulting in the anterior end of Stentor becoming rounded rather than cone-shaped. One hour after the start of regeneration, basal bodies begin to form at the locus of stripe contrast. After 3 hr, the first cilia of the new membranellar band are visible. These cilia show uncoordinated beating. After 5 hr, the new membranellar band elongates and extends along the anterior-posterior axis. A site for the new mouthparts is cleared at the posterior end of the membranellar band. During this stage, the cilia become oriented with respect to each other and their beating begins to become coordinated, forming multiple short metachronal waves. The nodes of the macronucleus begin to condense. By 6 hr, the mouthparts are completely formed and the macronucleus is fully condensed. At 7 hr the membranellar band and mouth migrate to the anterior end of the cell. The macronucleus extends into a sausage-like shape. By 8 hr after sucrose shock the Stentor is fully regenerated. The membranellar band completely wraps around the anterior of the cell, all of the oral cilia coordinate to form a single metachronal wave, the macronucleus is re-nodulated, and the cell resumes normal feeding activity. (B) Surgical bisection of Stentor. When a Stentor cell is cut in half perpendicular to the long axis, two cell fragments are produced, an anterior half-cell and a posterior half-cell. Immediately after cutting, both half-cells heal their wounded edges. The anterior half-cell then regenerates a new posterior body including the hold-fast, and the posterior half-cell regenerates a new anterior body including the oral apparatus (OA). Oral regeneration in the posterior half-cell has the same general morphological events and timing as oral regeneration in the sucrose-shocked cells. Both fragments are able to regenerate because the elongated macronucleus that is divided into both halves during surgery is highly polyploid, ensuring that each half-cell retains many copies of the genome. (C) Comparative transcriptional profiling. We performed RNA sequencing (RNAseq) on sucrose-shocked cells regenerating as in panel A, as well as on both the anterior and posterior half-cells regenerating after bisection as in panel B. These three datasets are represented by the three circles of the Venn diagram, with blue representing genes expressed during regeneration in bottom half-cells after bisection, green representing genes expressed during regeneration in top half-cells after bisection, and coral representing genes expressed during regeneration in cells following sucrose shock. Genes were grouped into modules according to correlated expression patterns shared between two or more fragments. For example, the ‘general regeneration’ module was defined based on genes showing differential expression in all three cases of regeneration (OA, anterior half, and posterior half).