Courtship behavior, communicative sound production and resistance to stress in Drosophila mutants with defective agnostic gene coding for LIMK1

To elucidate the role of one of the main elements of signal cascade of actin remodeling—LIM-kinase 1 (LIMK1)—in the control of animal behavior we have studied the characteristics of courtship behavior, parameters of acoustic communicative signals and their resistance to heat shock (HS, 37°C, 30 min) in Drosophila melanogaster males with the agnts3 mutation in the agnostic locus which contains CG1848 gene for LIMK1. The data obtained were compared with the results of our previous similar investigation on wild type CS males [1]. Flies were divided into 4 groups. The males of control groups were not subjected to heat shock. Other groups were comprised of males subjected to heat shock either at the beginning of larval development when the mushroom body neuroblasts are predominantly dividing (groups HS1), or at the prepupal stage when the brain central complex is developing (groups HS2), or at the imago stage 1 hour before the test (groups HS). All males were tested at the age of 5 days. Virgin and fertilized CS females were used as courtship objects. Comparison of control groups of the wild type (CS) and mutant strains has shown that the mutation agnts3 does not affect the main parameters of courtship behavior (courtship latency, the rapidity of achieving copulation, courtship efficiency) but leads to: a decrease in sexual activity, an increase in duration of sound trains in the songs and to a slight increase in the rate and stability of singing pacemakers. When compared to wild type, the agnts3 males are more resistant to HS given 1 hour before the test. After HS their courtship intensity does not decrease and the main parameters of their courtship behavior and communicative sound signals either do not change, or appear to be even better stabilized. The frequency of distorted sound pulses (an indicator of frequency of impairments in the activity pattern of neuro-motor circuits of the singing center) decreases, and the working rate and stability of pacemakers of the pulse and the sine songs increases. Therefore, although the sharply elevated LIMK1 and p-cofilin levels detected by immunofluorescent techniques in the cells of agnts3 mutants can lead to dramatic defects in learning and memory [2] accompanied by a decline of motivation of males, they do not appreciably affect the neuro-motor coordination during singing. The higher resistance of characteristics of the mutant behavior and communicative sound signals to heat shock is in agreement with the fact that the extremely high LIMK1 and P-cofilin levels fall down to normal values after HS and both the learning acquisition and memory formation are restored.