Judul: Expression of bZIP1 and LEC1 Genes and Lipid Content in  Microalgae Nannochloropsis sp. Cultures Under Salinity Stress
Abstrak: Mikroalga Nannochloropsis sp. merupakan kandidat penghasil bahan bakar berupa biofuel. Hal ini disebabkan, kemampuannya mengakumulasi lipid dalam jumlah tinggi, terutama pada kondisi cekaman. Pembentukan lipid dipengaruhi oleh faktor transkripsi berupa gen Basic Leucine Zipper 1 (bZIP1) dan Leafy Cotyledon 1 (LEC1). Penelitian ini bertujuan menganalisis ekspresi gen bZIP1 dan LEC1 dalam kultur mikroalga Nannochloropsis sp. pada kondisi cekaman salinitas dan hubungannya dengan biosintesis lipid. Isolat Nannochloropsis sp. dikultur pada kultur peralihan, kemudian pada kultur kontrol dan perlakuan cekaman salinitas tinggi dan rendah. Analisis ekspresi gen dilakukan dengan isolasi RNA, sintesis cDNA, dan analisis qRT-PCR. Pengukuran lainnya adalah densitas sel, bobot biomassa, dan kandungan lipid. Hasil qRT-PCR menunjukkan peningkatan secara signifikan ekspresi gen relatif bZIP1 sebesar 340 kali dan LEC1 sebesar 18.000 kali pada kultur Nannochloropsis sp. yang mengalami cekaman salinitas tinggi, dan sebaliknya hampir tidak terdeteksi pada kultur yang mengalami cekaman salinitas rendah dibandingkan kontrol. Densitas sel kultur mikroalga menurun pada perlakuan cekaman salinitas tinggi dan rendah berturut-turut sebesar 38,3% dan 16,3% saat fase stasioner, serta penurunan bobot biomassa berturut-turut sebesar 45,9% dan 40,8%. Kandungan lipid pada kultur mikroalga cekaman salinitas tinggi mengalami peningkatan sebesar 35,3% dan kandungan lipid pada kultur mikroalga cekaman salinitas rendah mengalami penurunan sebesar 34,4%., Nannochloropsis sp. is a promising candidate for producing biofuel, a substitute for fossil fuels. This is due to its ability to accumulate high levels of lipids, especially under stress conditions. Lipid formation is influenced by transcription factors such as Basic Leucine Zipper 1 (bZIP1) and Leafy Cotyledon 1 (LEC1). This study aims to analyze the expression of bZIP1 and LEC1 genes in Nannochloropsis sp. cultures under salinity stress conditions and their relationship with lipid biosynthesis. Nannochloropsis sp. isolates were initially cultured in transition culture, then subcultured in control and salinity stress conditions. Gene expression analysis involved RNA isolation, cDNA synthesis, and qRT-PCR. Cell density, biomass weight, and lipid content were assessed. qRT-PCR showed a significant increase in the relative gene expression of bZIP1 by 340 times and LEC1 by 18.000 times in Nannochloropsis sp. cultures under high salinity stress, while expression was almost undetectable under low salinity stress compared to the control. Cell density of Nannochloropsis sp. cultures decreased by 38,3% and 16,3% respectively, during the stationary phase, with biomass weight reductions of 45,9% and 40,8%, respectively. Lipid content in high salinity stress culture increased by 35.3%, while lipid content in low salinity stress cultures decreased by 34,4%.
Keyword: bZIP1, cekaman salinitas, faktor transkripsi, LEC1, triasilgliserol

Judul: Expression of Orthologous bZIP1 and LEC1 Genes Related to Lipid Biosynthesis in Microalgae Nannochloropsis oceanica under Nitrogen Deficiency Culture Conditions
Abstrak: Mikroalga dimanfaatkan sebagai bahan baku biodiesel karena kemampuannya mengakumulasi triasilgliserol (TAG) yang tinggi. Gen bZIP1 dan LEC1 diketahui sebagai faktor transkripsi yang terlibat dalam meregulasi metabolisme lipid dan peningkatan TAG. Penelitian ini bertujuan menganalisis ekspresi gen ortolog bZIP1 dan LEC1 pada Nannochloropsis oceanica dalam kondisi kultur defisiensi nitrogen menggunakan teknik Quantitative Real-Time PCR (qRT-PCR). Sampel N. oceanica dikultur pada media Walne dan diberi perlakuan kondisi defisiensi nitrogen dengan perbandingan antara kontrol dengan perlakuan adalah 4:1 dan konsentrasi akhir NaNO3 100 dan 25 mg/L. Isolat N. oceanica berbasis morfologi dikonfirmasi dengan teknik sekuensing pada dua fragmen gen 18s rRNA dan diyakini pada tingkat genus merupakan Nannochloropsis sp.. Gen-gen ortolog bZIP1 dan LEC1 pada N. oceanica dianalisis menggunakan algoritma Basic Local Alignment Search Tool (BLAST) berdasarkan kemiripan sekuens protein (BLASTp dan tBLASTn) pada database genus Nannochloropsis. Primer dirancang dari sekuens nukleotida kedua gen tersebut. Hasil analisis ekspresi relatif dengan teknik qRT-PCR menunjukkan adanya peningkatan signifikan ekspresi gen ortolog bZIP1 sebesar 10,8 kali lipatnya sementara LEC1 tidak signifikan hanya 1,2 kali pada perlakuan kultur defisiensi nitrogen. Penelitian ini diharapkan menambah informasi kandidat gen yang dapat direkayasa sehingga diekspresi berlebih pada N. oceanica untuk menghasilkan strain yang memiliki tingkat produksi TAG yang lebih tinggi., Microalgae are a promising biodiesel feedstock due to their ability to accumulate substantial amounts of triacylglycerols (TAG). The bZIP1 and LEC1 genes are crucial transcription factors, governing lipid metabolism and enhancing TAG accumulation. This research aims to investigate the expression of orthologous bZIP1 and LEC1 genes in Nannochloropsis oceanica under nitrogen deficiency culture conditions, employing Quantitative Real-Time PCR (qRT-PCR) technique. The N. oceanica samples were cultured in Walne’s medium and subjected to nitrogen deficiency conditions with a control-to-treatment ratio of 4:1 using final NaNO3 concentrations of 100 and 25 mg/L. Morphologically identified N. oceanica isolate was confirmed through sequencing of two 18s rRNA gene fragments, indicating its genus-level classification as Nannochloropsis sp. Orthologous bZIP1 and LEC1 genes in N. oceanica were analyzed using Basic Local Alignment Search Tool (BLAST) algorithm, specifically BLASTp and tBLASTn, based on protein sequence similarity within the Nannochloropsis genus database. Primers were designed from the nucleotide sequences of both genes. The qRT-PCR results revealed a significant 10,8-fold increase in the expression of the bZIP1 orthologous gene, while LEC1 showed non-statistically significant 1,2-fold increase under nitrogen deficiency. This study contributes valuable insights into potential candidate genes for genetic engineering to enhance TAG production in N. oceanica strains.
Keyword: bZIP1, LEC1, Microalgae, qRT-PCR, triacylglycerol

Judul: Penggunaan Teorema Homeomorphy 2-Manifold dan Teorema Euler Poincare pada Torus 𝑇�� dan Simplicial Complex 𝐾��
Abstrak: Two dimensional topological spaces are said to be homeomorphic if they have the same topological invariant, where one of topological invariant used is an Euler characteristic. Homeomorphy 2-Manifold’s Theorem and Euler Poincare’s Theorem are used to distinguish two topological spaces. Homeomorphy 2-Manifold’s Theorem uses Euler characteristic to identify two dimensional topological spaces. Euler Poincare’s Theorem is an alternative way to find Euler characteristic with Betti number, which is topological invariant as well. The objective of this paper is to investigate the homeomorphism of torus 𝑇����� and simplicial complex 𝐾�����. Topological space torus and simplicial complex 𝐾����� have the same Euler characteristic, which is two. Based on Homeomorphy 2-Manifold’s Theorem topological space torus 𝑇����� and simplicial complex 𝐾����� is homeomorphic.
Keyword: simplicial, torus, Euler, homeomorphism, topology