Pathogenesis-related (PR) proteins expression during IMI herbicide and ABT xenobiotic treatment in young sunflower roots

VEGA TATIANA; NESTARES GRACIELA; GIL MERCEDES

Toulouse

Simposio; Sunflower and climate change. International Symposium.; 2018

Plant response to environmental stresses is mediated by the regulation of gene expression. A major abiotic stress encountered by cultivated sunflower (Helianthus annuus L.) is application of several classes of herbicides, including the imidazolinones. Proteomic studies were carried out in order to characterize the plant response to imazethaphyr herbicide (IMI) in 15 day-old sunflower roots. Seeds of the HA89 sunflower inbred line were grown in pots filled with perlite and watered by capillarity with 1.1 g∙L−1 of Murashige and Skoog?s basal salts while incubated in controlled conditions (27±2 ºC, 16/8 hr light/dark). After 8 days, the plants were treated with 0 and 1 μM IMI and a combination of 1 µM IMI + 70 μM 1-aminobenzotriazole (ABT), a cytochrome P450s inhibitor. After 15 days, plants were collected and their roots were washed to remove perlite debris. Total root protein extracts were analyzed via liquid chromatography combined with electrospray tandem mass spectrometry on an LTQ Orbitrap (Thermo Fisher). Data were analized against the sunflower complete proteome sequences(1) and a set of commonly observed contaminants. Protein identification was performed using Proteome Discoverer (Thermo Fischer) and Max Quant software(2).Visualization of protein abundance was performed using Perseus software(3). Functional categorization was performed using MapMan software(4).Changes in protein expression levels (min. 2-fold) were detected in several metabolic pathways including aminoacid turnover, xenobiotic detoxification and cell wall synthesis. In addition, biotic stress-related proteins were highly expressed in response to IMI treatment. These protein families involved cell wall-located chitinases, PR-6 endopeptidases and endochitinase precursors, among others. All of them are reported to be involved in defense response to fungus and systemic acquired resistance. EP3-chitinases present in root epidermis and related to hypersensitive response, were also detected. In contrast, no expression changes were found in these protein families in response to ABT. Recent changes in climatic conditions all over the world and specifically in Argentina included a raise in annual precipitations, favouring the incidence of fungal pathogens. A rapid adaptation or innate tolerance mechanisms in sunflower would protect further development of the plant and would be important in fighting against emergent pathogens. PR-related proteins detected in this preliminary study included those involved in fungal defense suggesting that herbicide treatment triggers some stress response pathways shared with those ones corresponding to biotic stresses. Common plant defense mechanisms would play important roles in fighting against new pests, weeds, as well as abiotic stress in sunflower.