Judul: Identifikasi Dan Ekspresi Gen Protein Selubung Pepper Vein Yellows Virus Pada Escherichia Coli
Abstrak: Penyakit klorosis pada tanaman cabai yang disebabkan oleh Pepper vein yellows virus (PeVYV) anggota dari genus Polerovirus (famili Luteoviridae) telah ditemukan di Indonesia. Berdasarkan hasil survei yang dilakukan pada pertanaman cabai di Desa Kertha, Kecamatan Payangan, Kabupaten Gianyar, Provinsi Bali, tanaman cabai bergejala klorosis banyak ditemukan dalam intensitas tinggi. Tanaman sakit menunjukkan gejala kuning pada lamina, tetapi tulang daun tetap berwarna hijau. Sejauh ini belum tersedia secara komersial antiserum spesifik PeVYV untuk kepentingan deteksi, sehingga upaya membuat antiserum perlu dilakukan. Salah satu teknik terbaru dalam menyediakan sumber antigen untuk pembuatan antiserum ialah melalui teknik molekuler ekspresi gen protein selubung virus pada bakteri kompeten yang sesuai. Penelitian ini bertujuan untuk mengidentifikasi Pepper vein yellows virus (PeVYV) berdasarkan sifat penularan virus menggunakan Aphis nasturtii, bentuk dan ukuran partikel virus, deteksi RNA total dengan reverse transcription-polymerase chain reaction (RT-PCR), perunutan sekuen nukleotida, dan ekspresi gen protein selubung PeVYV pada bakteri ekspresi Escherichia coli. PeVYV dapat ditularkan dari tanaman cabai sakit ke tanaman cabai sehat oleh serangga A. nasturtii (Homoptera: Aphididae). Partikel PeVYV berbentuk heksagonal dengan diameter ~30 nm. RT-PCR menggunakan primer spesifik forward BamHI dan reverse PstI berhasil mengamplifikasi target gen protein selubung PeVYV berukuran ~650 pb. Sekuen gen protein selubung PeVYV isolat Bali, Indonesia memiliki homologi sebesar 99% dengan PeVYV isolat Jepang dan Taiwan. PeVYV berhasil dibuktikan sebagai penyebab penyakit klorosis pada tanaman cabai asal Bali, Indonesia. DNA CP-PeVYV dikloning pada vektor ekspresi pQE30 (Qiagen) pada situs enzim restriksi BamHI dan PstI untuk membentuk plasmid rekombinan pQE30-CP-PeVYV dengan fusi protein putatif. Optimasi ekspresi rekombinan CP-PeVYV dilakukan pada beberapa suhu inkubasi yang berbeda (25, 28, 30, dan 37 oC), konsentrasi akhir Isoprophyl-β-Dthiogalactoside (IPTG) (0.25, 0.5, dan 1 mM) dan waktu panen setelah diinduksi IPTG (3, 6, 9, 12, dan 15 jam). Gen protein selubung PeVYV berukuran ~650 pb diamplifikasi dengan primer spesifik, dikloning pada vektor ekspresi pQE30, ditransformasi, dan dikayakan ekspresi gen tersebut (overexpression) pada bakteri ekspresi E. coli strain M15[pREP4]. Analisis SDS-PAGE menunjukkan rekombinan gen protein selubung PeVYV berhasil terekspresi dengan pita protein putatif berukuran ~25 kDa setelah 6 jam diinduksi dengan 0.5 mM IPTG pada suhu 37 °C, tetapi perlu dioptimasi agar ekspresi gen melimpah. Penyediaan protein selubung PeVYV murni dapat digunakan sebagai imunogen pada tubuh mamalia (kelinci). Antibodi PeVYV yang terbentuk dapat digunakan sebagai bahan deteksi virus yang bersangkutan.
Keyword: Aphis nasturtii, cabai, coat protein, ekspresi, Indonesia, Pepper vein yellows virus (PeVYV), Polerovirus

Judul: Identifikasi Spesies Polerovirus Penyebab Penyakit Klorosis pada Tanaman Cabai Melalui Sekuen Nukleotida
Abstrak: During survey on chilli pepper in Kertha Vilage, Payangan Distric, Gianyar Regency, Bali Province, there were found that many chilli pepper plants showing virus like induced symptom of chlorosis. Leaves of diseased plant exhibited yellowing appearance with interveinal chlorosis but the vein still with normal green color. This disease symptom is different from that of induced by viruses had been reported present in Indonesia. The disease was similar with that of induced by Polerovirus reported from other countries. Thus, the attempt of identification was focused on Polerovirus by reverse transcription-polymerase chain reaction (RT-PCR) and nucleotida sequence. By using primer pair specific to Polerovirus that were CP-F (5’-AATTAAGGATCCAATACGGGAGGGGTT AGGAGAAAT-3’) and CP-R (5’-AATTAACTGCAGTTTCGGGTTGTGCAAT TGCACAGTA-3’). RT-PCR applications were successfully amplified a DNA band of about 650 bp from the diseased sample plants, but not from the asymptomatic one. The RT-PCR products were then directly sequenced. Using BLAST program, the nucleotide sequence of the virus isolate has a high homology (more than 90%) with those of Pepper vein yellows virus (PeVYV) from other countries. Thus, the virus associated with chlorosis disease on chilli pepper in Bali was identified as PeVYV. Phylogenetic tree analysis revealed that PeVYV from Bali has closed relationship with the virus isolates from Japan, Taiwan, Thailand, the Philippine, India and Mali.
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Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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