盐碱化对农业构成重大挑战,人为的全球变暖加剧了。生物兴奋剂,来自活的微生物或天然提取物,已经成为传统农业和有机农业的宝贵工具。然而,我们对生物刺激剂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。在这项研究中,我们采用了一种综合方法来研究在控制条件(正常浇水)和盐胁迫下联合应用植物生长促进细菌(巨大芽孢杆菌菌株BM08)和非微生物生物刺激剂的有效性。在确认两种条件下的产量增加后,我们通过测量许多生理参数(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。我们的发现表明,在盐胁迫条件下,微生物和非微生物生物刺激剂的联合作用导致抗氧化反应的降低和参与细胞分裂素生物合成的基因的上调。这个,反过来,导致更高浓度的生物活性细胞分裂素,异戊烯基腺苷,在根和叶中以及γ-氨基丁酸的增加,一种与非生物应激反应相关的非蛋白质氨基酸。此外,我们观察到苹果酸的减少,与SR激酶的脱落酸(ABA)无关的上调,与非生物应激反应相关的蛋白激酶家族。此外,我们观察到,在盐胁迫下,非微生物生物刺激剂的单次施用会触发ABA依赖性反应;然而,当与微生物生物刺激剂结合时,它加强了由BM08细菌菌株触发的机制。这项全面的研究表明,两种生物刺激剂的组合能够引起细胞分裂素依赖性反应,这可以解释在盐胁迫条件下观察到的产量增加。
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.