Significance of NatB-mediated N-terminal acetylation of auxin biosynthetic enzymes in maintaining auxin homeostasis in Arabidopsis thaliana.

The auxin IAA (Indole-3-acetic acid) plays key roles in regulating plant growth and development, which depends on an intricate homeostasis that is determined by the balance between its biosynthesis, metabolism and transport. YUC flavin monooxygenases catalyze the rate-limiting step of auxin biosynthesis via IPyA (indole pyruvic acid) and are critical targets in regulating auxin homeostasis. Despite of numerous reports on the transcriptional regulation of YUC genes, little is known about those at the post-translational protein level. Here, we show that loss of function of CKRC3/TCU2, the auxiliary subunit (Naa25) of Arabidopsis NatB, and/or of its catalytic subunit (Naa20), NBC, led to auxin-deficiency in plants. Experimental evidences show that CKRC3/TCU2 can interact with NBC to form a NatB complex, catalyzing the N-terminal acetylation (NTA) of YUC proteins for their intracellular stability to maintain normal auxin homeostasis in plants. Hence, our findings provide significantly new insight into the link between protein NTA and auxin biosynthesis in plants.

Natural Shrimp (Litopenaeus vannamei) Tropomyosin Shows Higher Allergic Properties than Recombinant Ones as Compared through SWATH-MS-Based Proteomics and Immunological Response.

Tropomyosin (TM) is the major shrimp allergen that could trigger anaphylactic reactions. Recently, recombinant TM (rTM) has been accepted widely in the field of allergen-specific immunotherapy, but the allergenicity of rTM has not been compared with natural TM (nTM) based on an in vitro digestion profile. In this work, IgG-/IgE binding, allergen peptides, and degranulation ability of the digested samples in simulated gastric fluid/simulated intestinal fluid/gastrointestinal models from nTM and rTM were evaluated by immunoassays, proteomics, and basophil degranulation assay. Results showed that pepsin-digested and trypsin-digested samples of rTM exhibited lower IgG-/IgE binding and degranulation than those of nTM. More peptides of the digested samples from rTM (57.8%) matched shrimp allergic epitopes than those from nTM (33.3%). However, the peptide SITDELDQTF (269-278) appeared most frequently. These findings would supply foundation data for epitope-based immunotherapy to shrimp allergic individuals.