Isolasi dan Karakterisasi Gen SiCCR1 terkait Biosintesis Lignin pada Hotong (Setaria italica [L.] Beauv) untuk Sifat Toleransi terhadap Cekaman Abiotik

Abstract

Hotong (Setaria italica [L.] Beauv) merupakan tanaman penghasil karbohidrat bernutrisi baik dengan toleransi terhadap cekaman kekeringan dan salinitas. Kandungan lignin di akar dan batang telah dilaporkan sebagai salah satu mekanisme penting toleransi tanaman terhadap cekaman kekeringan dan salinitas, dimana lignin berperan dalam ketegaran mekanik tanaman serta transportasi air dan solut melalui jaringan pembuluh. Cinnamoyl-CoA reductase (CCR) merupakan salah satu enzim kunci dalam lintasan biosintesis lignin. Penelitian ini bertujuan mengisolasi dan mengkarakterisasi gen penyandi CCR, SiCCR1, dari empat genotipe hotong dengan toleransi berbeda terhadap cekaman kekeringan dan salinitas. Gen SiCCR1 berhasil diisolasi dari DNA genom satu genotipe hotong toleran (ICERI-6) dan tiga genotipe hotong peka (NTB-1, Mauliru-2, dan Buru) dengan panjang basa nukleotida 2.293-2.296 pb. Pensejajaran dengan gen SiCCR1 referensi dari hotong kultivar IC-403579 menunjukkan terdapat synonymous SNP di intron 1 (basa 40, 41, 42) dan intron 4 (basa 1.398), dan satu non-synonymous SNP di ekson 6 (basa 2.336). SNP yang teridentifikasi pada gen SiCCR1 dari keempat genotipe hotong dalam penelitian ini belum dapat membedakan dengan konsisten genotipe toleran dan peka terhadap cekaman kekeringan dan salinitas.

Foxtail millet (Setaria italica [L.] Beauv) is one of the nutritious carbohydrate-producing crops with comparable tolerance to drought and salinity stresses. Lignin content in the roots and stems has been reported as one important mechanism in the tolerance to drought and salinity stresses, where lignin plays a role in the mechanical robustness of plants and facilitates the transportation of water and solutes through vascular tissue. Cinnamoyl-CoA reductase (CCR) is one of the key enzymes in the lignin biosynthesis pathway. This study aimed to isolate and characterize the CCR encoding gene, SiCCR1, from four foxtail millet genotypes differing in their drought- and salinity tolerance. SiCCR1 genes were successfully isolated from the genomic DNA of one tolerant genotype (ICERI-6) and three sensitive genotypes (NTB-1, Mauliru-2, and Buru) with the nucleotide length ranging from 2.293-2.296 bp. Alignment with the reference sequence of SiCCR1 from cv. IC-403579 (tolerant) showed synonymous SNPs in intron 1 (nt. 40, 41, and 42) and intron 4 (nt. 1.398), and a non-synonymous SNP in exon 6 (nt. 2.336). None of the identified SNPs were consistently associated with the tolerance level of the foxtail millet genotypes.