The phytochrome phy1 of Azospirillum brasilense Az39 is involved in bacteria response to red light under in vitro and in planta conditions.

MOLINA, ROMINA; CONIGLIO, ANAHÍ; NIEVAS, SOFÍA; TORRES, DANIELA; MORA, VERÓNICA; CASSÁN, FABRICIO

Montevideo

Congreso; XXX Reunión Latinoamericana de Rizobiología. V Conferencia Latinoamericana de Microorganismos Promotores del Crecimiento Vegetal.; 2021

Asociación Latinoamericana de Rizobiología (ALAR)

A. brasilense Az39 is a non-photosynthetic bacterium extensively used as activeprinciple of inoculants formulated for both seeds and foliar treatment. In thiswork, we analyzed the in vitro and in planta behavior of Az39 and the phytochrome(phy1) deficient mutant Az39Δphy1 exposed to red (RL),blue (BL) or day (DL) light. For in vitroassays, pure cultures of both bacteria with a title of 1.109cfu/ml weredecimally diluted, spreaded on Luria Bertani or MMAB agar plates and individuallyexposed to RL, BL, DL or maintained in darkness (O) at 36 or 28 °C respectively.The in planta experiments were performedby foliar inoculation of soybean seedlings at V3 stage with 1.105 cfu/mlof each bacterium. After inoculation, seedlings were exposed to RL, BL, DL or Ountil the end of the experiment. Periodically, the number of viable cellsrecovered from light-exposed soybean leaves was obtained. Our resultsdemonstrated that DL and BL were lethal for both Az39 and Az39Δphy1 when they grew in LB medium at 36 or 28°C. Furthermore, DL and BL werelethal for Az39 in both culture media at 28°C while the mutant was able togrowth in similar experimental conditions. Contrary, Az39Δphy1 was unable to grow in MMAB medium exposed to LR at 28°C while Az39 did. Under in planta conditions, a higher bacterialsensitivity was observed to RL for Az39Δphy1 which was recovered from soybean leaves up to 24 h post-inoculation incomparison to Az39 recovered until 96 h post-inoculation. These results suggestthat tolerance of Az39 to LR depends of the presence and functionality of thephytochrome coded by phy1. Additionally,both the nutritional composition of culture medium and incubation temperature wereable to modify the bacterial tolerance to DL and BL.