Transcriptomic analysis of drought responsive genes in transgenic chickpea overexpressing DREB1A

Abstract:

Leading plant molecular biologists have long argued that constitutive overexpression of transcription factors can activate entire stress-response gene networks more efficiently than single-gene insertions. This research tested that premise by profiling the transcriptome of transgenic chickpea (Cicer arietinum L., cv. Pusa 362) constitutively expressing the Arabidopsis DREB1A gene under the control of the CaMV 35S promoter. Leaf tissue was sampled from transgenic (T₃ generation) and wild-type plants at 0, 6, 24, and 72 hours after withholding irrigation in a controlled-environment facility at Birsa Agricultural University, Ranchi. RNA-Seq on the Illumina NovaSeq 6000 platform generated 38.4 to 47.1 million paired-end reads per sample. Differential expression analysis identified 1,847 genes significantly upregulated (log₂FC ≥ 2, FDR < 0.01) in the transgenic line at 24 hours of drought, compared with 412 genes in the wild type. The DREB1A transgene itself showed 24.7-fold induction. Key downstream targets—LEA3, P5CS, RD29A, and SOD-Cu—were upregulated 5.9 to 18.3-fold in the transgenic versus 1.1 to 3.2-fold in the wild type. Gene ontology enrichment highlighted osmotic adjustment, reactive oxygen species scavenging, and protein protection as the three most activated functional categories. Proline accumulation in transgenic leaves was 3.4-fold higher than in the wild type at 72 hours. These results confirm that DREB1A overexpression in chickpea activates a broad drought-tolerance network and identify candidate downstream genes for marker-assisted selection.