Maize drought protection by Azospirillum argentinense Az19 requires bacterial trehalose accumulation

Azospirillum argentinense Az19 is an osmotolerant plant growth-promoting bacterium that protects maize plants from drought. In this work, we explored the role of trehalose in the superior performance of Az19 under stress. The trehalase-coding gene treF was constitutively expressed in Az19 through a miniTn7 system. The resulting recombinant strain, Az19F, did not accumulate trehalose, was affected in its capacity to cope with salt-, osmotic-, and UV-stress, and showed higher reactive oxygen species levels. Physiological alterations were also observed under normal conditions, such as increased growth in biofilms, higher motility, and decreased auxin secretion. Even so, the capacity of Az19F to colonize maize roots was not affected, either under normal or drought conditions. When inoculated in maize, both Az19 and Az19F strains promoted plant growth similarly under normal irrigation. However, unlike Az19, the trehalose-deficient strain Az19F could not improve the height, aerial fresh weight, or relative water content of maize plants under drought. Notably, Az19F triggered an exacerbated oxidative response in the plants, resulting in higher levels of antioxidant and phenolic compounds. We conclude that the role of trehalose metabolism in A. argentinense Az19 transcends stress tolerance, being also important for normal bacterial physiology and its plant growth-promoting activity under drought.

Instituto de Microbiología y Zoología Agrícola (IMYZA)

Fil: Garcia, Julia Elena. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Microbiología y Zoología Agrícola (IMyZA); Argentina

Fil: Pagnussat, Luciana Anabella. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Pagnussat, Luciana Anabella. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto de Investigaciones en Biodiversidad y Biotecnología (INBIOTEC); Argentina

Fil: Amenta, Melina B. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Casanovas, E. Mabel. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Diaz, Pablo R. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Diaz, Pablo R. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina

Fil: Labarthe, María Mercedes. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Labarthe, María Mercedes. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina

Fil: Martino, María V. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Groppa, María Daniela. Universidad de Buenos Aires (UBA). Instituto de Química y Fisicoquímica Biológicas (IQUIFIB); Argentina

Fil: Groppa, María Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET). Instituto de Química y Fisicoquímica Biológicas (IQUIFIB); Argentina

Fil: Creus, Cecilia Mónica. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Maroniche, Guillermo Andrés. Universidad Nacional de Mar del Plata (UNMdP). Facultad de Ciencias Agrarias; Argentina

Fil: Maroniche, Guillermo Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Argentina