Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València-Consejo Superior de Investigaciones Científicas, Valencia, 46022, Spain.
Caldic Ibérica, S.L., Barcelona, 08210, Spain.
J Integr Plant Biol. 2024 Oct;66(10):2140-2157. doi: 10.1111/jipb.13755. Epub 2024 Aug 7.
Salinization poses a significant challenge in agriculture, exacerbated by anthropogenic global warming. Biostimulants, derived from living microorganisms or natural extracts, have emerged as valuable tools for conventional and organic agriculture. However, our understanding of the molecular mechanisms underlying the effects of biostimulants is very limited, especially in crops under real cultivation conditions. In this study, we adopted an integrative approach to investigate the effectiveness of the combined application of plant growth-promoting bacterium (Bacillus megaterium strain BM08) and a non-microbial biostimulant under control conditions (normal watering) and salt stress. After confirming the yield increase under both conditions, we investigated the molecular mechanisms underlying the observed effect by measuring a number of physiological parameters (i.e., lipid peroxidation, antioxidants, chlorophylls, total phenolics and phytohormone content), as well as RNA sequencing and primary metabolite analyses. Our findings reveal that the combined effect of the microbial and non-microbial biostimulants led to a decrease in the antioxidant response and an up-regulation of genes involved in cytokinin biosynthesis under salt stress conditions. This, in turn, resulted in a higher concentration of the bioactive cytokinin, isopentenyladenosine, in roots and leaves and an increase in γ-aminobutyric acid, a non-proteic amino acid related to abiotic stress responses. In addition, we observed a decrease in malic acid, along with an abscisic acid (ABA)-independent up-regulation of SR-kinases, a family of protein kinases associated with abiotic stress responses. Furthermore, we observed that the single application of the non-microbial biostimulant triggers an ABA-dependent response under salt stress; however, when combined with the microbial biostimulant, it potentiated the mechanisms triggered by the BM08 bacterial strain. This comprehensive investigation shows that the combination of two biostimulants is able to elicit a cytokinin-dependent response that may explain the observed yield increase under salt stress conditions.
盐渍化是农业面临的重大挑战，而人为全球变暖则加剧了这一挑战。生物刺激素来源于活微生物或天然提取物，已成为常规和有机农业的重要工具。然而，我们对生物刺激素作用的分子机制的理解非常有限，特别是在实际种植条件下的作物中。在这项研究中，我们采用综合方法研究了在对照条件（正常浇水）和盐胁迫下联合应用植物促生菌（巨大芽孢杆菌菌株 BM08）和非微生物生物刺激素的效果。在确认两种条件下均能提高产量后，我们通过测量一些生理参数（即脂质过氧化、抗氧化剂、叶绿素、总酚和植物激素含量）以及 RNA 测序和初级代谢物分析，研究了观察到的效果的分子机制。我们的研究结果表明，微生物和非微生物生物刺激素的联合作用导致抗氧化反应的减少，以及在盐胁迫条件下细胞分裂素生物合成相关基因的上调。这反过来又导致生物活性细胞分裂素异戊烯基腺苷在根和叶中的浓度增加，并增加与非生物胁迫反应有关的非蛋白氨基酸γ-氨基丁酸。此外，我们观察到苹果酸的减少，同时 SR-激酶（与非生物胁迫反应相关的蛋白激酶家族）的 ABA 独立上调。此外，我们观察到单独应用非微生物生物刺激素在盐胁迫下会引发 ABA 依赖性反应；然而，当与微生物生物刺激素联合应用时，它增强了 BM08 细菌菌株引发的机制。这项全面的研究表明，两种生物刺激素的组合能够引发细胞分裂素依赖性反应，这可能解释了在盐胁迫条件下观察到的产量增加。
