Molecular characterization and expression profiling of NADH-ubiquinone reductase Complex 1 MLRQ Subunit in Pennisetum glaucum

MLRQ is a subunit of nicotinamide adenine dinucleotide hydride (NADH)-ubiquinone reductase complex 1, the largest complex of the respiratory chain in the mitochondria. In this study, the PgMLRQ gene from pearl millet Pennisetum glaucum subsp. monodii (Maire) Brunken was sequenced and characterized to examine its expression under stress and during germination. The sequenced cDNA for PgMLRQ was 493 bp, containing an open reading frame of 282 bp. The translated protein is 94 amino acids length and contained a B12D domain from 5 to 73 amino acids. Transmembrane helix prediction revealed the deduced PgMLRQ protein accommodates transmembrane helix spanning from 14 to 30 amino acids embedded in the mitochondrion membrane. Transmembrane topology indicated that the hydrophobic N-terminal of the PgMLRQ protein was found outside the membrane while the C-terminal was inside the membrane. Quantitative real-time PCR revealed high expression of PgMLRQ in flowers during heading, whereas the expression in shoots, roots, and seeds of 5-day-old seedlings and spikes before ripening was low. Moreover, the expression of PgMLRQ in seedlings root under salt and short exposure to cold was substantially higher than shoots and seeds. However, exposure to drought during germination resulted in expression in roots lower than in shoots and seeds. The results of this study help to uncover of the role of the MLRQ in response to stress during P. glaucum growth.