TI - Rok and myosin are not necessary for the maintenance or remodeling of formed AJs . AB - Active Rho regulates cellular responses through binding to and activating downstream effector proteins/enzymes . Two major effectors of active Rho are the Rho kinases and diaphanous proteins , both of which have only one member in Drosophila . Rok is a serine/threonine kinase that activates the myosin light chain ( MLC ) , leading to increased myosin activity and actomyosin contractility ( Conti and Adelstein , 2008 ) . To determine the role of the Rho1-Rok-myosin axis in mature pupal eye epithelium morphogenesis , MARCM clones of the rok2-null allele , spaghetti squash sqhAX3 , a null allele of the Drosophila homologue of MLC and zip1 , a null allele of Drosophila myosin heavy chain zipper , were generated . In all instances , single cell clones had an increased apical cell area similar to Rho172 clones ( Fig 4 , a , c , and d ; and Table S1 ) . However , in contrast to Rho172 clones , in multiple neighboring null clones , all AJs were completely intact ( Fig 4 , b-d ) . The rok2 and Rho172 clonal cells exhibited an equivalent decrease of MLC PHOSphorylation ( Fig S2 , i and j ; and Table S3 ) , indicating that Rok activity was decreased equally in rok2 and Rho172 clones . Decreased MLC activity in sqhAX3 clones was confirmed by immunofluorescence with a PHOSphorylated MLC antibody ( Fig 4 c'' ) . The absence of myosin heavy chain in zip1 clones was confirmed by immunofluorescence ( Fig 4 d'' ) . These results indicated that the Rho1-Rok-myosin axis was necessary to maintain appropriate apical cell tension but not required to maintain/remodel formed AJs .