Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
Example: Context: Architecturally, the school has a Catholic character. Atop the Main Building's gold dome is a golden statue of the Virgin Mary. Immediately in front of the Main Building and facing it, is a copper statue of Christ with arms upraised with the legend 'Venite Ad Me Omnes'. Next to the Main Building is the Basilica of the Sacred Heart. Immediately behind the basilica is the Grotto, a Marian place of prayer and reflection. It is a replica of the grotto at Lourdes, France where the Virgin Mary reputedly appeared to Saint Bernadette Soubirous in 1858. At the end of the main drive (and in a direct line that connects through 3 statues and the Gold Dome), is a simple, modern stone statue of Mary.
Question: To whom did the Virgin Mary allegedly appear in 1858 in Lourdes France?
Example solution: Saint Bernadette Soubirous
Example explanation: This is the correct answer. Because the question is asking for the name of the person and following sentence from the passage answers it: It is a replica of the grotto at Lourdes, France where the Virgin Mary reputedly appeared to Saint Bernadette Soubirous in 1858.

Problem: Context: Protein-protein interactions are essential for many cellular processes. We have developed a technology called light-activated dimerization (LAD) to artificially induce protein hetero- and homodimerization in live cells using light. Using the FKF1 and GIGANTEA (GI) proteins of Arabidopsis thaliana, we have generated protein tags whose interaction is controlled by blue light. We demonstrated the utility of this system with LAD constructs that can recruit the small G-protein Rac1 to the plasma membrane and induce the local formation of lamellipodia in response to focal illumination. We also generated a light-activated transcription factor by fusing domains of GI and FKF1 to the DNA binding domain of Gal4 and the transactivation domain of VP16, respectively, showing that this technology is easily adapted to other systems. These studies set the stage for the development of light-regulated signaling molecules for controlling receptor activation, synapse formation and other signaling events in organisms.
Question: Which G protein is essential in the formation and function of lamellipodia?
Solution: rac1