Abstract
Background
We aimed to gain insight into the response mechanism of alfalfa to drought stress by recognizing and analyzing drought-responsive genes in the roots of different root types of alfalfa. The rhizomatous-rooted M. sativa ‘Qingshui’ (or QS), tap-rooted M. sativa ‘Longdong’ (or LD), and creeping-rooted M. varia ‘Gongnong No. 4’ (or GN) were used to simulate drought stress with PEG-6000 and analyze the transcriptome information and physiological characteristics of the root system.
Results
It was found that aridity caused a significant increase in the content of osmotic stress substances and antioxidant enzyme activity. The content of malondialdehyde (MDA) in QS was lower than that in LD and GN under stress conditions, indicating a stronger accumulation capacity of osmotic regulatory substances. Based on sequencing results, 14,475, 9,336, and 9,243 upregulated DEGs from QS, LD, and GN were annotated into 26, 29, and 28 transcription factor families, respectively. QS showed more DEGs than LD and GN. KEGG enrichment analysis identified that DEGs were significantly enriched in metabolic pathways such as amino acid biosynthesis, phenylpropanoid biosynthesis, plant hormone signaling transduction, and MAPK pathways. This suggests a strong correlation between these pathways and drought stress. Simultaneously, it was discovered that genes associated with ABA hormone signaling (MS. gene93372, MS. gene072046, and MS. gene012975) are crucial for adapting to drought stress.
Conclusions
These genes, such as serine/threonine protein kinases and abscisic acid receptors, play a crucial role in plant hormone signaling and MAPK pathways. They could serve as potential candidate genes for drought resistance research in alfalfa, providing a molecular foundation for studying drought resistance.