The field of plant sphingolipid biology has evolved in recent years. Sphingolipids are abundant in cell membranes, and genetic analyses revealed essential roles for these lipids in plant growth, development, and responses to abiotic and biotic stress. Salicylic acid (SA) is a key signaling molecule that is required for induction of defense-related genes and rapid and localized cell death at the site of pathogen infection (hypersensitive response) during incompatible host–pathogen interactions. Conceivably, while levels of SA rapidly increase upon pathogen infection for defense activation, they must be tightly regulated during plant growth and development in the absence of pathogens. Genetic and biochemical evidence suggest that the sphingolipid intermediates, long-chain sphingoid bases, and ceramides, play a role in regulating SA accumulation in plant cells. However, how signals generated from the perturbation of these key sphingolipid intermediates are transduced into the activation of the SA pathway has long remained to be an interesting open question. At least four types of molecules – MAP kinase 6, reactive oxygen species, free calcium, and nitric oxide – could constitute a mechanistic link between sphingolipid metabolism and SA accumulation and signaling.

24Corn infected with Ustilago maydis, causal agent of common smut disease, produces galls that 25 are used as food in certain cultures, but may be contaminated with mycotoxins. The objective of 26 this study was to determine mycotoxin levels in common smut galls (CSGs) collected from the 27 field at corn ear reproductive stages R1 through R5 and in commercial CSGs products. The study 28 was conducted in 2012 and 2013. A simple extraction method for five mycotoxins was devised 29 and the results showed the presence of these compounds in CSGs in corn during ear development 30 at various physiological stages. Fumonisin was the major mycotoxin in CSG samples in both 31 2012 (63%, ≤150.7 μg g -1 ) and 2013 (46.9%, ≤20.9 μg g -1 ); followed by aflatoxin (2012: 2%, 32 ≤14.7 ng g -1 ; 2013: 30.6%, ≤10.8 ng g -1 ) and zearalenone (2012: ≤41.70 ng g -1 ; 2013: ≤12.40 33 ng g -1 ). Deoxynivalenol (DON) was only detected in 2012 (≤1.6 μg g -1 ), and cyclopiazonic acid 34 was only detected in 2013 (≤3.18 μg g -1 ). Commercial canned and fresh CSG samples also 35 contained detectable amounts of mycotoxins including aflatoxin, fumonisin, CPA, and DON. 36Aspergillus flavus was isolated from selected 2013 CSG field samples at R2 or older (0-1.6 x 10 6 37 cfu/g), whereas Fusarium spp were isolated at R1 or older (0-7.5 x 10 7 cfu/g). These results 38 indicate that CSGs can be infected with mycotoxigenic fungi and contaminated with mycotoxins. 39The incidence of mycotoxins in commercially available CSG products was highly variable and 40 warrants further study. 41

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