Summary The brain of Drosophila melanogaster contains ca. 150 circadian neurons [1] functionally divided into Morning and Evening cells that control peaks in daily behavioral activity at dawn and dusk, respectively [2, 3]. The PIGMENT-DISPERSING FACTOR (PDF) positive small ventral Lateral Neurons (sLNvs) promote morning behavior, while the PDF negative sLNv and the dorsal Lateral Neurons (LNds) generate evening activity. Much less is known about the ca. 120 Dorsal Neurons (DN1, 2 and 3). Using a Clk-GAL4 driver that specifically targets a subset of DN1s, we generated mosaic per0 flies with clock function restored only in these neurons. We found that the Clk4.1M-GAL4 positive DN1s promote only morning activity under standard (high light intensity) light:dark cycles. Surprisingly however, these circadian neurons generate a robust evening peak of activity under a temperature cycle in constant darkness. Using different light intensities and ambient temperatures, we resolved this apparent paradox. The DN1 behavioral output is under both photic and thermal regulation. High light intensity suppresses DN1-generated evening activity. Low temperature inhibits morning behavior, but it promotes evening activity under high light intensity. Thus, the Clk4.1M-GAL4 positive DN1s, or the neurons they target, integrate light and temperature inputs to control locomotor rhythms. Our study therefore reveals a novel mechanism contributing to the plasticity of circadian behavior.

Summary Light is a crucial input for circadian clocks. In Drosophila, short light exposure can robustly shift the phase of circadian behavior. The model for this resetting posits that circadian photoreception is cell-autonomous: CRYPTOCHROME senses light, binds to TIMELESS (TIM) and promotes its degradation, mediated by JETLAG (JET). However, it was recently proposed that interactions between circadian neurons are also required for phase resetting. We identify two groups of neurons critical for circadian photoreception: the Morning (M)- and the Evening (E)-oscillators. These neurons work synergistically to reset rhythmic behavior. JET promotes acute TIM degradation cell-autonomously in M- and E-oscillators, but also non-autonomously in E-oscillators when expressed in M-oscillators. Thus, upon light exposure, the M-oscillators communicate with the E-oscillators. Since the M-oscillators drive circadian behavior, they must also receive inputs from the E-oscillators. Hence, although photic TIM degradation is largely cell-autonomous, neural cooperation between M- and E-oscillators is critical for circadian behavioral photoresponses.

SU1MHARYThe =r2&pbhUj genome contains three major sequenoes related to the v-.A gene. Previously published molecular studies have confirmed the structural homology between v-Ar and two of the Droskph1aa sequences. We have sequenced a portion of the third v-gUM-related DroaolhUA gene and found that it also shares structural homology with vertebrate and Drosowb±A =-family genes. RNA sequences from each of the = genes are present in pre-blastoderm embryos indicating that they are of maternal origin. As embryogenesis prooeeds, the levels of each of the are RNA sequences decline. The pre-blastoderm = gene transcripts contain poly(A) and are present on polyribosomes suggesting that they are functional mRKAs. Sinoe the DrkQgRW.a Arg transcripts were maternally inherited, we also investigated their distribution in adult females. The majority of the a transcripts in adult females were contained in ovaries. Only low levels of the transcripts were detected in males. These results strongly suggest that an abundant supply of Ac protein is required during early embryogenesis, perhaps at the time of cellularization of the blastoderm-nuclei. INTRODUCTNThe genomes of lower eukaryotes such as DrosoUhila and yeast contain sequences related to vertebrate onoogenes (1,2,3,4). Thus it is possible to study cellular oncogene structure and function in different developmental and genetic contexts. V-= gene sequences, representing one of the most extensively studied oncogene families, are among those sequences that are conserved in DlosobIA. Recombinant DNA clones representing three 1rwnb±1a genomic sequences complementary to the v-= gene have been reported (5,6). Nucleotide sequence analysis has confirmed that the v-=-complementarity of two of these genomic sequences is due to significant structural homology, (7) while the third has remained uncharacterized. The studies described in this report were initiated to fill two voids in the knowledge of Droso2LU± =-related sequences; the lack of nucleotide sequence data from the third =-related genomic segment and the lack of detailed knowledge of the expression of the three =-related-genomic C) I RL Press Umited, Oxford, England. Nucleic Acids ResearchVolume 13 Number 6 1985 2 153

Vertebrate genomes contain an extensive family of genes possessing varying degrees of homology to the v-src oncogene. Most src-related proteins identified to date are intracellular and membrane-associated, although some are transmembrane proteins and function as receptors for peptide growth factors. Three Drosophila gene sequences related to the v-src gene have been identified, each exhibiting a high degree of homology to one or more of the src-family members encoding an intracellular protein. We have isolated a panel of cloned Drosophila sequences exhibiting weak v-src hybridization and were interested to determine whether any members of this group represented homologues of additional known src-family genes, especially those functioning as growth factor receptors. As we report here, four of these clones, representing overlapping portions of the same genomic segment, hybridized preferentially with the v-erb-B oncogene and were further characterized. The deduced amino-acid sequence from a portion of this Drosophila genomic segment is 77% homologous to the kinase domain of human epidermal growth factor (EGF) receptor, a substantially greater degree of homology than was observed with any other known src-family member. By hybridization with a human EGF receptor complementary DNA clone probe, we demonstrate that the same genomic segment showing homology with the kinase domain also contains sequences related to the extracellular domain of the EGF receptor gene.

Drosophila melanogaster genomic sequences that hybridize with v-myc have been reported (B.-Z. Shilo and R. A. Weinberg, Proc. Natl. Acad. Sci. U.S. A. 78:6789-6792, 1981). We have detected Drosophila RNA sequences that also hybridize with v-myc. In an attempt to characterize these RNA sequences, we used v-myc hybridization probes to isolate Drosophila genomic seg'ments. None Despite the lack of structural homology between the Drosophila and v-myc sequences, the initial results of our investigations into the pattern of expression of the v-mychybridizing RNA species were novel enough to warrant their completion. Polyadenylic acid-containing transcripts complementary to v-myc and to the Drosophila genomic segments have been detected in embryos, pupae, adults, and Kc cells and on polyribosomes in Kc cells, suggesting that the Drosophila genomic sequences exist in the form of functional genes. We have found that certain transcripts are present in preblastoderm embryos and that their levels fall during midembryogenesis and remain low during the 4 days of larval life. These transcripts reappear during metamorphosis and are present in adults at low levels. In adults, the embryo RNA species are detectable only in ovaries. These results indicate that the early embryonic transcripts are of maternal origin and that their expression may play a role in early development. MATERIALS AND METHODSCell and animal culture. The Drosophila Kco cell line (Kc) was maintained on D20 medium (13) (GIBCO Laboratories) containing 5% fetal calf serum (GIBCO Laboratories). Cell lines were maintained in monolayer cultures at 25°C. An Oregon R strain of D. melanogaster was used as the source of RNA for all developmental stages analyzed. The sources of the RNA preparations (see Fig. 6) were as follows. Embryos were from an 18-h nonsynchronized collection. Pupae were collected from the walls of culture bottles at 160 h after egg deposition. Synchronization of the pupae was achieved by limiting the time for egg deposition to 2 h. The age of adult flies used for RNA was not controlled. 7 on May 9, 2018 by guest