Sexual behavior in Drosophila melanogaster flies is greatly influenced by chemical cues. In this study, a spatial distribution of female and male sex pheromones was investigated on the surface of virgin and mated six-day-old fruit flies. Surface analysis was performed using the technique of mass spectrometry imaging (MSI) matrix-assisted laser desorption/ionization – time of flight (MALDI-TOF) and confirmed by gas chromatography – mass spectrometry (GC-MS) analysis of hexane extracts prepared from dissected flies. MALDI-TOF MSI experiments focused on female pheromones (7Z,11Z)-heptacosa-7,11-diene (7,11-HD) and (7Z,11Z)-nonacosa-7,11-diene (7,11-ND) were enhanced by using lithium 2,5-dihydroxybenzoate (LiDHB) matrix to improve the ionization and quality of MS spectra. Oxygenated compounds represented by male anti-attractants 11-cis-vaccenyl acetate (cVA) and 3-O-acetyl-1,3-dihydroxy-octacosa-11,19-diene (CH503) were successfully ionized without MALDI matrix in the form of potassium adducts in laser desorption ionization (LDI-TOF MSI) mode. A similar pattern of distribution for 7,11-HD and 7,11-ND was observed on the surface of both the left and the right female wing, with the strongest signals at the base of the wing. 7,11-HD and 7,11-ND were additionally detected on female legs but not on the body. The distribution of both male pheromones, cVA and CH503, was localized in virgin male flies solely on the abdominal tip and anogenital region. In addition, results from MSI experiments with mated flies showed the distribution of cVA and CH503 also on the female abdomen and thorax, demonstrating that anti-attractants were transferred from males to females during copulation. Results from LDI/MALDI-TOF MSI were supported by GC-MS analysis of hexane extracts prepared from different parts of virgin male or female Drosophila flies. Similar amounts of 7,11-HD and 7,11-ND were present on the legs, body and wings (127 ± 5 ng and 170 ± 8 ng, respectively). cVA was detected only on the male body. All acquired MSI datasets were affected by mass shift (predominantly between ±0.2 Da to ±0.4 Da), which was reduced using a mass recalibration approach. The LDI/MALDI-TOF MSI technique makes it possible to study the distribution of female and male sexual pheromones on D. melanogaster flies. Moreover, the technique enables the transfer of male sex pheromones to females during copulation to be visualized. However, imaging experiments of 3-D biological samples performed on a single TOF-MS instrument equipped with a MALDI ion source and UV nitrogen laser evinced a photo-electric charging/discharging, a phenomenon that often leads to unpredictable mass shifts and poor mass accuracy.

中文翻译：

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果蝇果蝇化学生态学的再探：质谱成像在整个原始和交配的蝇上性信息素的二维分布图

果蝇果蝇的性行为受化学提示的影响很大。在这项研究中，研究了原始和交配的六日龄果蝇表面上雌性和雄性性信息素的空间分布。使用质谱成像（MSI）基质辅助的激光解吸/电离-飞行时间（MALDI-TOF）技术进行表面分析，并通过气相色谱-质谱（GC-MS）分析对从解剖后制备的己烷提取物进行分析苍蝇。MALDI-TOF MSI实验着重于雌性信息素（7Z，11Z）-庚7-7,11-二烯（7,11-HD）和（7Z，11Z）-壬酸7,11-二烯（7,11-ND）通过使用2,5-二羟基苯甲酸锂（LiDHB）基质来增强离子束，以改善质谱的电离和质量。以雄性抗吸引剂11-顺式-异戊烯基乙酸酯（cVA）和3-O-乙酰基-1,3-二羟基-辛酸-11,19-二烯（CH503）为代表的含氧化合物在没有MALDI基质的情况下成功电离激光解吸电离（LDI-TOF MSI）模式下的钾加合物。在左，右雌机翼的表面都观察到类似的7,11-HD和7,11-ND分布模式，其中最强的信号位于机翼的底部。另外在女性腿部检测到7,11-HD和7,11-ND，但在身体上未检测到。雄性信息素cVA和CH503的分布均定位于仅在腹尖和肛门生殖器区域的原始雄性蝇中。此外，通过MSI交配蝇实验获得的结果表明，cVA和CH503也分布在雌性腹部和胸部，证明了在交配期间抗诱剂从雄性转移到雌性。LDI / MALDI-TOF MSI的结果得到GC-MS分析的支持，该分析是从原始雄性或雌性果蝇的不同部位制备的己烷提取物的。在腿，身体和翅膀上也有相似量的7,11-HD和7,11-ND（分别为127±5 ng和170±8 ng）。仅在男性身上检测到cVA。所有采集的MSI数据集都受到质量偏移的影响（主要在±0.2 Da到±0.4 Da之间），使用质量重新校准方法可以降低质量偏移。LDI / MALDI-TOF MSI技术使研究黑腹果蝇的雌性和雄性性信息素的分布成为可能。此外，该技术使得在交配过程中将男性信息素转移至女性的过程得以可视化。然而，