Characterization of β-amino- and γ-amino butyric acid-induced citrus seeds germination under salinity using nanoLC-MS/MS analysis.

KEY MESSAGE: BABA or GABA induces salinity acclimation during citrus seeds germination via alternation of specific proteins (e.g., citrin). The impact of four elicitors, namely hydrogen peroxide (H2O2), β-amino butyric acid (BABA), γ-amino butyric acid (GABA) and hydrogen sulfide (H2S) donor, sodium hydrosulfide (NaHS), in citrus seed germination under salinity (150 mM NaCl) was tested. The germination potential was adversely affected by NaCl-alone treatment. Pretreatment with H2O2 or the NaHS-H2S donor prior to salinity had no significant effect in germination process, however, BABA and GABA substantially improved seed acclimation to salinity, as evidenced by increased germination percentage and radicle length. Total soluble proteins of radicle and cotyledons were separated by 1DE SDS-PAGE and proteins zones were analyzed by mass spectrometry. In total, 27 and 3 proteins were identified in radicle and cotyledons, respectively. The identified proteins mainly include redox-regulated enzymes (i.e., glutathione S-transferase, dehydroascorbate reductase, Mn-superoxide dismutase, glutathione peroxidase), energy-related proteins (i.e., isocitrate lyase, malate synthase, pyruvate decarboxylase), stress proteins (i.e., stress-related protein, miraculin, thaumatin, disulfide isomerase), storage proteins (i.e., vicilin, Pis v 1 allergen 2S albumin) and transcriptional regulators (i.e., MarR family transcriptional regulator, MADS544 protein). Pretreatments with BABA or GABA altered the accumulation of protein zones exclusively corresponding to citrin, indicating that this protein may serve as a marker for salinity acclimation in citrus seeds.