Changes of protein profile in Zizania latifolia during cooling storage

Abstract: The changes of protein profile in postharvest Z. latifolia during cooling storage at 1°C for 0 (control), 15 and 30 days were investigated to study the molecular mechanism of senescence of postharvest Zizania latifoliausing two-dimensional electrophoresis (2-DE). The results showed that a total of about 650 protein spots were detected on the gels in which 35 spots showed a significant (p<0.05) change in protein abundance based on the two-fold difference. 29 spots were identified using MALDI-TOF/TOF. We classified these 29 protein spots into six functional categories: metabolism (20.7%), cell structure (27.6%), stress response and defense (20.7%), senescence (6.9%), protein synthesis (13.8%) and unknown functional proteins (10.3%). 15 spots were up-regulated while 14 spots were down-regulated among 29 differentially expressed proteins spots. For 15 up-regulated spots, spot 9 (adenosine kinase), spot 23 (glycosyl hydrolases family 17) and spot 27 (transketolase) were related to metabolism; spot 1 (profiling), spot 6 (β-1,3-glucanase precursor), spot 7 (glucan endo-1,3-beta-glucosidase), spot 8 (β-1,3-glucanase precursor), spot 24 (xyloglucan endotransglycosylases) and spot 39 (β-1,3-glucanase) were related to cell structure; spot 17 (universal stress protein family), spot 30 (thaumatin-like protein isoform 2), spot 32 (glutathione S-transferase) and spot 48 (dehydroascorbate reductase) were related to stress response and defense; spot 22 (cysteine protease) and spot 33 (papain-like cysteine proteinase) were related to senescence. For 14 down-regulated spots, spot 36 (diphosphonucleotide phosphatase 1), spot 44 (enolase) and spot 53 (isocitrate dehydrogenase) were related to metabolism; spot 25 (actin) and spot 38 (actin depolymerisation factor/cofilin -like domains) were related to cell structure; spot 31 (hipI-SODC1s) and spot 49 (chitinase class I) were related to stress response and defense; spot 15 (glycine-rich RNA-binding protein), spot 18 (putative chaperonin 21 precursor), spot 21 (putative ribosomal protein S12) and spot 56 (ubiquitin-conjugating enzyme E2) were related to protein synthesis; spot 43 (WD40 domain), spot 51 (unknown protein) and spot 55 (band_7_prohibitin) were unknown functional proteins. The most important proteins that behave differentially are related to senescence in postharvest Z. latifolia were β-1,3-glucanase precursor (spot 6, spot 8), adenosine kinase (spot 9), universal stress protein family (spot 17), cysteine protease (spot 22), glycosyl hydrolases family 17 (spot 23), hipI-SODC1s (spot 31), glutathione S-transferase (spot 32), papain-like cysteine proteinase (spot 33), β-1,3-glucanase (spot 39), dehydroascorbate reductase (spot 48) and chitinase class I (spot 49). These protein's functions mainly concentrated on material and energy metabolism, stress response and defense, cell structure and senescence. These results indicated that the senescence of postharvest Z. latifolia may be caused by multi-actions including the regulation of material metabolism, change of energy metabolism pathway, decline of reactive oxygen scavenging capacity and degradation of cell structure. This study provided experimental data and come up with new perspectives for the mechanism of postharvest Z. latifolia senescence. However, the molecular biological analysis and subcellular proteomic studies need to be further investigated in the future.