Transcriptome Analysis Reveals the Vital Role of ABA Plays in Drought Tolerance of the ABA-Insensitive Alfalfa (Medicago sativa L.)

Abstract

Drought stress severely affects alfalfa (Medicago sativa L.) growth and production. It is particularly important to analyze the key networks of drought in alfalfa through physiological and molecular levels. However, how to quickly screen drought-tolerant alfalfa germplasm and how to elucidate the molecular pathways of alfalfa responding to drought are less studied. In this study, based on our previous research, we further verified the association between the heritability of ABA sensitivity during seed germination and drought tolerance of plants and identified the key pathways of drought tolerance differences between ABA-sensitivity (S1-0) and -insensitivity (S1-50) plants via RNA-seq and analysis. The results showed that the sensitivity to ABA in alfalfa seeds can be inherited and that plants that are insensitive to ABA during germination show stronger drought tolerance. An analysis of the differentially expressed genes (DEGs) revealed that ABA biosynthesis and signaling, amino acid metabolism, LEA, and wax synthesis-related pathways may be the key pathways that can be used for drought tolerance improvement in alfalfa. DEGs such as NCED, PYR/PYL, and PP2C may contribute to drought tolerance in the S1-50 plant. The study further confirms that screening with ABA at the seed germination stage can select alfalfa lines with good drought tolerance, which provides a new theoretical basis for alfalfa drought tolerance breeding. The expression of the key genes of alfalfa in response to drought stress was also tested.

Research on drought stress in Medicago sativa L. from 1998 to 2023: a bibliometric analysis

“…Research has shown that the ABA content in alfalfa varies between roots and leaves under drought conditions and is influenced by the duration of the stress ( Ren and He, 2010 ; Gamal et al., 2016 ). The plants that were not sensitive to ABA during germination showed stronger drought tolerance ( Xu et al., 2024 ). Additionally, the accumulation of ABA in alfalfa under drought stress is related to the dynamics of storage proteins, gene expression, and the accumulation of certain osmoregulatory substances in the primary roots ( Li et al., 2015 ).Overall, these physiological and biochemical responses collectively enhance alfalfa’s ability to withstand drought conditions, highlighting the complexity and adaptability of this crop in response to water stress.…”

“…further demonstrated that the miR156/SPL13 module alleviates drought stress in alfalfa through tissue-dependent regulatory molecules and physiological processes ( Fang et al., 2023 ). Moreover, the sensitivity of alfalfa seeds to ABA is heritable, and screening for ABA during seed germination can help select alfalfa lines with better drought tolerance ( Xu et al., 2024 ).…”