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Karyotype and Male Pre-Reductional Meiosis of the Sharpshooter Tapajosa Rubromarginata (Hemiptera: Cicadellidae)

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Karyotype and Male Pre-Reductional Meiosis of the Sharpshooter Tapajosa Rubromarginata (Hemiptera: Cicadellidae) Symbol.dfont in 8/10 pts abcdefghijklmopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ Symbol.dfont in 10/12 pts abcdefghijklmopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ Symbol.dfont in 12/14 pts abcdefghijklmopqrstuvwxyz ABCDEFGHIJKLMNOPQRSTUVWXYZ Karyotype and male pre-reductional meiosis of the sharpshooter Tapajosa rubromarginata (Hemiptera: Cicadellidae) Graciela R. de Bigliardo1,2, Eduardo Gabriel Virla3, Sara Caro1 & Santiago Murillo Dasso1 1. Facultad de Ciencias Naturales e IML. U.N.T. Miguel Lillo 205. San Miguel de Tucumán (4000), Tucumán, Argentina; [email protected] Karyotype and male pre-reductional meiosis of the 2. Fundación Miguel Lillo. Miguel Lillo 251. San Miguel de Tucumán (4000), Tucumán, Argentina; sharpshooter Tapajosa rubromarginata (Hemiptera: [email protected] Cicadellidae) 3. PROIMI-Biotechnology, Biocontrol Div. Av. Belgrano & Pje. Caseros. San Miguel de Tucumán (4000), Tucumán, Graciela R. de Bigliardo, Eduardo Gabriel Virla, Sara Caro & Argentina; [email protected] Santiago Murillo Dasso Received 12-IV-2010. Corrected 17-IX-2010. Accepted 19-X-2010. [email protected]; [email protected]; evirla@hotmail. com Abstract: Cicadellidae in one of the best represented families in the Neotropical Region, and the tribe Proconiini comprises most of the xylem-feeding insects, including the majority of the known vectors of xylem-born phy- topathogenic organisms. The cytogenetics of the Proconiini remains largely unexplored. We studied males of Tapajosa rubromarginata (Signoret) collected at El Manantial (Tucumán, Argentina) on native spontaneous vegetation where Sorghum halepense predominates. Conventional cytogenetic techniques were used in order to describe the karyotype and male meiosis of this sharpshooter. T. rubromarginata has a male karyological formula of 2n=21 and a sex chromosome system XO:XX ( : ). The chromosomes do not have a primary constriction, being holokinetic and the meiosis is pre-reductional, showing similar behavior both for autosomes and sex chromosomes during anaphase I. For this stage, chromosomes are parallel to the acromatic spindle with kinetic activities in the telomeres. They segregate reductionally in the anaphase I, and towards the equator during the second division of the meiosis. This is the first contribution to cytogenetic aspects on proconines sharpshooters, particularly on this economic relevant Auchenorrhyncha species. Rev. Biol. Trop. 59 (1): 309- 314. Epub 2011 March 01. Key words: Insecta, Cicadellidae, Proconiini, karyotype, holokinetic chromosomes, sex chromosomes. Cicadellidae (Hemiptera: Auchenorhyn- 2008). The Proconiini (sharpshooters) is one cha) is a large family that includes approximate- of the largest groups of xylem-feeding insects ly 22 000 species, which is well represented in and includes the majority of the known vec- the Neotropical region (McKamey 2002). Due tors of xylem-born phytopathogenic organ- to their feeding habits and well-known capacity isms (Rakitov & Dietrich 2001, Redak et al. to transmit plant pathogens, some species rep- 2004). Tapajosa rubromarginata Signoret is resent significant pests for many economically distributed in tropical and subtropical areas important crops (Freytag & Sharkey 2002). of Brazil and Argentina (Paradell 1995, de The tribe Proconiini (Cicadellinae) is Azevedo-Filho & Carvallo 2004, Takiya & composed of 59 genera and over 400 spe- Dimitriev 2008). It has been collected from cies, all confined to the Americas (Young 15 host plants, Avena sativa (cultivated oat), 1968, Rakitov & Dietrich 2001), even though Saccharum officinalis (sugarcane), Sorghum Homalodisca vitripennis (Germar) has recently halepense (Johnson grass), Zea mays (corn), invaded Pacific Islands (Grandgirard et al. Tritricum aestivun (wheat), Bromus unioloides Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 59 (1): 309-314, March 2011 309 (rescuegrass) (Poaceae), Dahlia pinnata (dahl- MATERIAL AND METHODS ia) (Asteraceae), Tabebuia lapacho (yellow palmer trumpettree) (Bignoniaceae), Ipomaea Males of T. rubromarginata were obtained sp. (Concolvulaceae), Glycine max (soybean), from a wild population inhabiting a corn agroecosystem and its surrounding vegeta- Medicago sativa (alfalfa) (Fabaceae) Populus tion composed mostly of Sorghum halepense sp. (poplar) (Salicaceae), Lantana camara (lan- (L.) Pers, at El Manantial, Tucumán province tana), Hibiscus sp. (Verbenaceae), and Citrus (26°49’50.2” S - 65°16’59.4” W, elevation sinensis (Rutaceae) (de Azevedo-Filho & Car- 495m). Individuals were sexed by external valho 2004, Remes Lenicov et al. 1998, Remes characters, and confirmed later by the morphol- Lenicov et al. 2004, Virla et al. 2007). This ogy of their gonads. The testes, obtained form species is associated with grasslands and spon- 15 individuals, were preserved in a freshly- taneous weeds, and looses in sugar cane and prepared mixture of methanol/glacial acetic corn crops in Northwestern Argentina (Costilla acid (3:1) at 2-4ºC under dark conditions. et al. 1972, Remes Lenicov et al. 1998, Virla For the analysis of meiotic cells, the tes- et al. 2007). ticular follicles were processed by using the Cytogenetic studies on Auchenorrhyncha squash technique and then stained according began from Boring (1907) who analyzed sper- to the conventional Feulgen method by using matogenesis in 22 species. Recently, some con- Schiff reactive after an acid hydrolysis with tributions have been made (Halkka 1957, 1959, 1N HCL (hydrochloric acid) at 65ºC for 25min 1960a,b, de Lello et al. 1982, Kuznetsova et (Feulgen & Rosenbech 1924). al. 2003, 2009, Nokkala et al. 2004) but there The slides were examined with a Zeiss still a noticeable lack of information for several Axiolab microscope, and micrographs were groups. Fulgoroidea is the most studied super- obtained by using a MOTICAM 1 000 digi- family, and the reported chromosome numbers tal camera. In this study, approximately 1 range from 2n=19(XO) to 2n=37(XO) in males 000 nuclei from cells showing various mei- (Maryanska-Nadachowska et al. 2006). Most otic stages were used. Voucher specimens were of the species have 2n=26(XY), 2n=27 (XO) or deposited in the entomological collections of M. Lillo Institute (Tucumán, Argentina) 2n=29(XO), with a manifest preponderance of the latter complement (Halkka 1959, Kuznetso- va et al. 1998). In Auchenorrhyncha the XO RESULTS system is predominates and the XY system is secondary (Kuznetsova et al. 1998). Cicadel- T. rubromarginata presents a male karyo- type formula of 2n=21(20+X). During meiotic lidae, like other Auchenorrhyncha, have holo- stages, 10 bivalents and a univalent X chromo- kinetic chromosomes, showing highly variable some were observed. Among the bivalent there numbers in their karyotype. This type of chro- is little difference in size. The bivalents showed mosome plays an essential role in karyotype few chromosomes decreasing in size. The size evolution, due to the high levels of fragmenta- of the X chromosome is similar to the middle tion and fusions (Maryanska-Nadachowska et autosome pair, none of them have a primary al. 2006). constriction, thus being holokinetic. Proconiini cytogenetics remains largely In meiotic cells, from leptotene to diakine- unexplored; in addition, this subject is totally sis stages, the X chromosome shows positive unknown for Argentinian Auchenorrhyncha heteropycnosis, and is usually located outside species. The aim of this contribution is to report the autosomal chromatin mass (Fig. 1A). In the the chromosome number in T. rubromarginata, beginning of prophase I, leptotene/zygotene, it and provide a brief description of holokinetic is possible to see the heteropycnotic body; it chromosomes behavior during male meiosis. should be separate, but is located in the nucleus 310 Rev. Biol. Trop. (Int. J. Trop. Biol. ISSN-0034-7744) Vol. 59 (1): 309-314, March 2011 Fig. 1. Meiotic chromosomes of males of T. rubromarginata 2n=21 (20A+X0): (A) Leptotene with X chromosome placed outside chromatine mass (arrow). (B) Pachitene: chromosome pairing. The arrow show a heteropycnotic body (Bar:10 μm). (C) Diakinesis with chromosomes showing terminal and subterminal chiasmata (arrows). Arrowheads point signal an association between autosomes (Bar:10 μm). periphery. This can be seen until the end of The autosomes, as well as the X chromo- pachytene (Fig. 1B). In pachytene the chromo- some, segregate reductionally in anaphase I somes are completely paired (Fig. 1B) and, in and divided equationally during the second diplotene, they form 10 autosomal bivalents. division. Each homologue chromosome is In diplotene/diakinesis some the autosomal oriented parallel to the achromatic spindle, bivalents shows telomeric associations (Fig. thus the telomeric regions are active in meio- 1C). In addition, during diakinesis, the auto- sis I, while the X chromosome is observed somal bivalents change their staining affinities as univalent (Fig. 2A). In telophase I, ten so when they reach metaphase I, isopycnosis is autosomes move towards each pole after highly noticeable. At this stage, the autosomal reductional division while the X chromo- bivalents normally exhibit only one or two some lags behind, but finally reach one of the chiasmata located in different localization: ter- poles (Fig. 2B). minal, subterminal or interstitial. Because the Figure 2C represents a metaphase II nucle- ring shape of the bivalents, the presence of two us, with 10 autosomes and the noticeable uni- chiasmata is suggested (Fig. 1C). valent X chromosome. In the second
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