The yeast Papiliotrema laurentii alleviates drought-induced stress in maize and affects oxidative status, LEA genes, hormone concentrations, and fatty acid allocation

Drought stress can significantly affect maize growth; hence, new substances with a potential to alleviate drought-induced damage in plants are being investigated. Here, we studied the biostimulant potential and mechanisms of the yeast Papiliotrema laurentii CCY 17-3-24. The maize grains were treated with P. laurentii suspensions of different yeast concentrations (10 6 , 10 7 , 10 8 , and 10 9 cells ml -1 ) during the imbibition and germination. The yeast did not have plant-growth promoting effects in well-watered plants; however, it stimulated the growth of the drought-stressed maize in the concentration 10⁷ cells ml -1 (e.g., shoot dry weight by 21.6%). Furthermore, the relative water content and oxidative stress were improved in plants treated with the yeast compared to drought-stressed plants (e.g., decreased H 2 O 2 concentration by 46.1% in roots). The expression of LEA genes, which can be triggered by hormones, was significantly downregulated in yeast-treated plants compared to untreated plants. Although the yeast-treated plants showed slightly improved hormone concentrations (IAA, ABA) in drought compared to untreated plants (IAA concentration increased approximately by 19%), the action of P. laurentii was not likely connected to its ability to produce hormones, neither its ability to change the accumulation of proline. However, based on the oleaginous nature of P. laurentii , its positive influence on plants suffering from drought can be possibly explained by the production of fatty acids and their uptake by plants. This was supported by the increased concentration of fatty acids, especially in the roots of the yeast-treated plants (by 205.3%). • Optimal yeast concentration for drought alleviation in maize was 10 7 cells ml -1 • Stress markers were decreased in maize roots by yeast treatment • Yeasts did not improve maize growth through LEA gene upregulation • Concentration of phytohormones was modified by yeast treatment • Fatty acids produced by yeasts might be associated with plant defence against drought