Morphological screening and expression of droughtrelated genes P5SC1 and DREB1A in water-stressed pearl millet (Pennisetum glaucum) at the pre-fruiting stage

ABSTRACT

This study characterized 33 pearl millet accessions for drought tolerance and expression patterns of drought-related genes (P5CS and DREB1A) at the pre-fruiting stage. The accessions were evaluated for variability and screened for drought tolerance. Five weeks after sowing, we screened the pearl millet accessions for morpho-agronomic variability and to determine their tolerance to water stress over 14 days. From these screenings, we identified the most and least tolerant accessions (NGB00886 and NGB00885, respectively) for gene expression studies. To determine the expression pattern of the DREB1A and P5CS genes, RNA was extracted from leaf samples and converted to cDNA for analysis via quantitative real-time polymerase chain reaction. The study found significant variation (p > 0.05) in morphological traits among the pearl millet accessions. The principal component analysis showed three components accounted for over 90% of the variance. Additionally, there were significant (p < 0.01, p > 0.05) correlations among the plant growth attributes of the accessions. At genetic index 15, the accessions were grouped into five distinct clusters corresponding to their genetic similarities. Gene expression studies showed differences in the Ct values of the reference gene (ACT1) against the target genes. The expression pattern showed that DREB1A was up-regulated in the most tolerant and down-regulated in the least tolerant, while P5CS was up-regulated in both accessions. The study concluded that there are morphological variations among the accessions in response to water stress at the pre-fruiting stage, and the up- and down-regulation of DREB1A and P5CS genes are involved in the mechanism of regulation of water stress modulations in pearl millet.

Key words germplasm; drought tolerance; pearl millet; quantitative real-time polymerase chain reaction; reference genes