Pecan (Carya illinoinensis) kernels have a high phenolics content and a high antioxidant capacity compared to other nuts—traits that have attracted great interest of late. Changes in the total phenolic content (TPC), condensed tannins (CT), total flavonoid content (TFC), five individual phenolics, and antioxidant capacity of five pecan cultivars were investigated during the process of kernel ripening. Ultra-performance liquid chromatography coupled with quadruple time-of-flight mass (UPLC-Q/TOF-MS) was also used to analyze the phenolics profiles in mixed pecan kernels. TPC, CT, TFC, individual phenolics, and antioxidant capacity were changed in similar patterns, with values highest at the water or milk stages, lowest at milk or dough stages, and slightly varied at kernel stages. Forty phenolics were tentatively identified in pecan kernels, of which two were first reported in the genus Carya, six were first reported in Carya illinoinensis, and one was first reported in its kernel. The findings on these new phenolic compounds provide proof of the high antioxidant capacity of pecan kernels.

Calmodulin (CaM) regulates plant disease responses through its downstream calmodulin-binding proteins (CaMBPs) often by affecting the biosynthesis or signaling of phytohormones, such as jasmonic acid (JA) and salicylic acid. However, how these CaMBPs mediate plant hormones and other stress resistance-related signaling remains largely unknown. In this study, we conducted analyses in Arabidopsis (Arabidopsis thaliana) on the functions of AtIQM1 (IQ-Motif Containing Protein1), a Ca 21-independent CaMBP, in JA biosynthesis and defense against the necrotrophic pathogen Botrytis cinerea using molecular, biochemical, and genetic analyses. IQM1 directly interacted with and promoted CATALASE2 (CAT2) expression and CAT2 enzyme activity and indirectly increased the activity of the JA biosynthetic enzymes ACX2 and ACX3 through CAT2, thereby positively regulating JA content and B. cinerea resistance. In addition, in vitro assays showed that in the presence of CaM5, IQM1 further enhanced the activity of CAT2, suggesting that CaM5 may affect the activity of CAT2 by combining with IQM1 in the absence of Ca 21. Our data indicate that IQM1 is a key regulatory factor in signaling of plant disease responses mediated by JA. The study also provides new insights that CaMBP may play a critical role in the cross talk of multiple signaling pathways in the context of plant defense processes.

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A previous report showed that both Pyruvate decarboxylase (PDC) genes were significantly upregulated in kiwifruit after waterlogging treatment using Illumina sequencing technology, and that the kiwifruit AdPDC1 gene was required during waterlogging, but might not be required during other environmental stresses. Here, the function of another PDC gene, named AdPDC2, was analyzed. The expression of the AdPDC2 gene was determined using qRT-PCR, and the results showed that the expression levels of AdPDC2 in the reproductive organs were much higher than those in the nutritive organs. Waterlogging, NaCl, and heat could induce the expression of AdPDC2. Overexpression of kiwifruit AdPDC2 in transgenic Arabidopsis enhanced resistance to waterlogging and heat stresses in five-week-old seedlings, but could not enhance resistance to NaCl and mannitol stresses at the seed germination stage and in early seedlings. These results suggested that the kiwifruit AdPDC2 gene may play an important role in waterlogging resistance and heat stresses in kiwifruit.

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