To study tendon development, sr reporter expression was studied during leg development relative to and odd reporter, which is expressed at the segmental joints. The first tendon to develop is the long tendon of the tarsi that arises from cells coexpressing sr and odd at the T5/pretarsus boundary at early third instar. These cells invaginate and elongate into the tarsal cavity formed by the progressive evagination of the leg disc at the beginning of metamorphosis. By the end of leg development, they will form a long internal tube extending from pre-tarsus to femur with the apical pole facing the lumen. With a short delay, another cluster of tendon precursor cells is specified during the third instar at the femur/tibia boundary in the dorsal position. Subsequently, during early pupation, additional sr-positive clusters are specified along the five segmental pre-patterned odd-positive boundary rings. This indicates that odd/sr-positive tendon precursors are specified progressively following the leg proximodistal segmentation with odd expression preceding sr expression. N was observed to appear sequentially and precede sr expression.
Drives expression in tendon cells.
Larval expression is observed in tendon cells.
Pupal expression is observed in the attachment sites of the anterior dorsal medial muscles.