A DIGE proteomic analysis of wheat flag leaf treated with TERRA-SORB® foliar, a free amino acid high content biostimulant

Abstract

The flag leaf is the most important source of carbohydrate during wheat kernel filling. Around a 75% of all sugars stored in the kernel come from carbon fixed by this leaf. Terra-Sorb® foliar is an L-α-amino acid-based product from enzymatic hydrolysis for foliar application with a high ratio of free to total amino acids. Previous agronomical studies carried out on grassy, horticultural and tree crops have shown that the application of Terra-Sorb® increases photosynthetic plant activity and chlorophyll content, promotes rapid recovery from stress and improves fruit set. In this work, we have undertaken a proteomic approach to explore molecular mechanisms potentially involved in the stimulating effect of Terra-Sorb® Foliar on wheat yield when applied in commercial fields. Wheat plants at the flag leaf stage were treated, and a DIGE approach was used to compare the proteomes of treated vs. control plants in four biological replicates. Thirty-seven protein spots were found to change in abundance (ANOVA p<0.05) out of which 8 were down-regulated and 29 up-regulated in treated leaves. Twenty protein spots (1.2<fold change <1.9) encoded by 11 different genes were successfully identified by nLC-ESI-MS/MS and NCBInr database search. The deregulated proteins identified were mainly related to the life cycle of Rubisco. Importantly, two proteins involved in the positive regulation of Rubisco activity, namely Rubisco activase, and the large subunit of Rubisco binding protein, were found up-regulated in treated plants, suggesting a better performance of Rubisco. Down-regulated proteins were of metabolic and anti-stress enzymes, including Cu/Zn superoxide dismutase that protects photosystem 11 from photooxidation. In conclusion, significant changes were shown to occur in the wheat flag leaf proteome upon Terra-Sorb® Foliar application. The deregulated proteins identified are directly or indirectly involved in the C02 fixation which may correlate with the known stimulating effect of Terra-Sorb® Foliar of wheat yield, although further functional experiments are needed to validate the proposed hypothesis.