Imbibition of wheat seeds with polyamines modulates the interconvertions of citokinins forms in the seedling stage

NM GOMEZ MANSUR; N DE DIEGO; L SPÍCHAL; S CAVAR; O NOVÁK; MP BENAVIDES; SM GALLEGO

Virtual

Congreso; LVII Reunión Anual de SAIB y XVI Congreso Anual de la Asociación Civil de Microbiología General (SAMIGE).; 2021

SAIB

Successful germination in the early stages of seedling development is a crucial step in the growth of a new plant. Seed pre-soaking with different chemical agents has been associated with positive impacts on these stages. Previous research in our lab demonstrated that the imbibition of wheat (Triticum aestivum L) seeds with polyamines (PAs) increased primary root length. The biology of PAs and cytokinins (CK) seems to possess many overlapping functions, like cell proliferation, seed germination, and cell development. To understand the molecular and biochemistry mechanisms underlying those effects, PAs and CK metabolites were determined in root and leaves of wheat seedlings. For this objective seeds were soaked in distilled water (C) or 25µM spermine (Spm), spermidine (Spd), or putrescine (Put) for 3h in an orbital shaker (24±2°C, in darkness). After germinating on wet filter paper for 30 h (24±2°C, darkness), seedlings were transferred to pots with vermiculite (3 seedlings per pot), and at least 8 pots per treatment were prepared for each experiment. Plants were grown in a growth chamber (14/10h light/dark, 24±2°C, 60% RH) and irrigated with diluted (1/4) Hoagland's nutrient solution. After 6 d, plants were harvested. Seedlings that were treated with PAs showed an improved root length and a higher index vigor than C ones. In leaves, Put incremented endogenous diamine propane (DAP), cadaverine (Cad), Put, Spd, Spm and their conjugated pairs levels. Treatment with Spd did not show differences in Spd and Spm. On the other hand, Spm decreased the analyzed PAs. In roots, all PAs had a similar effect increasing total and free Cad. To evaluate the homeostasis of CK, thirty (30) metabolites corresponding to the different CK fractions and types were determined. In C leaves, the most abundant CK fraction corresponds to the O-glycosides (49%), followed by the bases (30%), the ribosides (18%), and the minor fraction was constituted by the N-glucosides (3%), nucleotide precursors were undetected. In the root, the total CK content doubled that of the leaf, and 11% was in the form of nucleotide precursor, 12% free base, 17% ribosides, 56% O-glycosides, and 4% N-glycosides. The amount found for each fraction is within the range predicted for monocots. About the types of CK, cZ was the majority in both tissues (more than 90% of the total), followed by iP and tZ, and finally DHZ (less than 1%). The imbibition with PAs altered CK metabolism. In common the three PAs decreased CK precursors and increased ribosides. Our results show that although all polyamines behaved as biostimulant agents in wheat, each one exerts this effect through its molecular mechanism. Modulation of endogenous PA balance, as well as the, modify of the interconversions among individual forms of CK, form part of the adjustment of seedling metabolism during post-germinative growth. New studies are currently being developed to decipher the mechanisms involved in the action of each PA.