Integrative transcriptome and metabolome analysis reveals the mechanisms of light-induced pigmentation in purple waxy maize

Introduction

Waxy maize, mainly consumed at the immature stage, is a staple and vegetable food in Asia. The pigmentation in the kernel of purple waxy maize enhances its nutritional and market values. Light, a critical environmental factor, affects anthocyanin biosynthesis and results in pigmentation in different parts of plants, including in the kernel. SWL502 is a light-sensitive waxy maize inbred line with purple kernel color, but the regulatory mechanism of pigmentation in the kernel resulting in purple color is still unknown.

Methods

In this study, cyanidin, peonidin, and pelargonidin were identified as the main anthocyanin components in SWL502, evaluated by the ultra-performance liquid chromatography (UPLC) method. Investigation of pigment accumulation in the kernel of SWL502 was performed at 12, 17, and 22 days after pollination (DAP) under both dark and light treatment conditions via transcriptome and metabolome analyses.

Results

Dark treatment affected genes and metabolites associated with metabolic pathways of amino acid, carbohydrate, lipid, and galactose, biosynthesis of phenylpropanoid and terpenoid backbone, and ABC transporters. The expression of anthocyanin biosynthesis genes, such as 4CL2, CHS, F3H, and UGT, was reduced under dark treatment. Dynamic changes were identified in genes and metabolites by time-series analysis. The genes and metabolites involved in photosynthesis and purine metabolism were altered in light treatment, and the expression of genes and metabolites associated with carotenoid biosynthesis, sphingolipid metabolism, MAPK signaling pathway, and plant hormone signal transduction pathway were induced by dark treatment. Light treatment increased the expression level of major transcription factors such as LRL1, myc7, bHLH125, PIF1, BH093, PIL5, MYBS1, and BH074 in purple waxy maize kernels, while dark treatment greatly promoted the expression level of transcription factors RVE6, MYB4, MY1R1, and MYB145.

Discussion

This study is the first report to investigate the effects of light on waxy maize kernel pigmentation and the underlying mechanism at both transcriptome and metabolome levels, and the results from this study are valuable for future research to better understand the effects of light on the regulation of plant growth.

Aflatoxins in Cereals and Cereal-Based Products: Occurrence, Toxicity, Impact on Human Health, and Their Detoxification and Management Strategies

Cereals and cereal-based products are primary sources of nutrition across the world. However, contamination of these foods with aflatoxins (AFs), secondary metabolites produced by several fungal species, has raised serious concerns. AF generation in innate substrates is influenced by several parameters, including the substrate type, fungus species, moisture content, minerals, humidity, temperature, and physical injury to the kernels. Consumption of AF-contaminated cereals and cereal-based products can lead to both acute and chronic health issues related to physical and mental maturity, reproduction, and the nervous system. Therefore, the precise detection methods, detoxification, and management strategies of AFs in cereal and cereal-based products are crucial for food safety as well as consumer health. Hence, this review provides a brief overview of the occurrence, chemical characteristics, biosynthetic processes, health hazards, and detection techniques of AFs, along with a focus on detoxification and management strategies that could be implemented for food safety and security.

Near-infrared spectroscopy to assess mycotoxins contamination and nutritional composition of maize marketed in South America, years 2020-2021

Mycotoxicological and nutritional analyses were conducted in maize from Argentina, Bolivia, Brazil (stratified by region), Colombia and Peru through near-infrared spectroscopy (NIRS) in 2020 and 2021. Concentrations of aflatoxin B1 (AFB1), fumonisins B1 + B2 (FBs), zearalenone (ZEN) and deoxynivalenol, in addition to water activity, crude protein (CP), ether extract (EE), starch and apparent metabolizable energy (AME) in poultry, were determined in 18,363 spectra (totalling 195,486 analyses). FBs were the most prevalent metabolites in South American maize, being detected in 91.6 and 91.9% of the samples; ZEN had the second highest positivity, 15.4 and 26.8%, followed by AFB1, 15.3 and 14.6% (2020 and 2021, respectively). FBs also had the highest incidence in Brazilian maize, 92.6 and 92.1%, followed by AFB1, 15.2 and 13.5%, and ZEN, 14.7 and 27.7% (2020 and 2021, respectively). Contamination with at least one mycotoxin was detected in 93.5% of the samples. The mycotoxins found co-contaminating the maize belong to the genera Fusarium and Aspergillus; FBs, followed by ZEN and AFB1, were the most prevalent toxins in the associations. Levels of water activity were below 0.70. Regarding chemical composition, CP presented the largest oscillation in relation to the mean in South American maize (both years). As for the Brazilian samples, the Southeast region showed the greatest positive variability in relation to the means for all evaluated parameters, followed by the Northeast region (excepting CP) in 2020; in 2021, the Central-West and Northeast regions had the highest levels of EE and AME. In both years, the South region presented lower levels in relation to the mean for most parameters. Data on prevalence, mycotoxicological contamination, storage conditions and nutritional quality of maize assist the decision-making process of raw material use. In this setting, NIRS suits the needs of the industry for providing information on multiple parameters in real time.

Distribution, toxicity, interactive effects, and detection of ochratoxin and deoxynivalenol in food: A review

Mycotoxins are secondary metabolites of fungi that cause severe damage to agricultural products and food in the food supply chain. These detrimental pollutants have been directly linked with poor socioeconomic patterns and human health issues. Among the natural micropollutants, ochratoxin A (OTA) and deoxynivalenol (DON) are widely distributed in food materials. The primary occurrence of these mycotoxins is reported in almost all cereal grains and fresh agro-products. Both mycotoxins have shown harmful effects, such as nephrotoxic, hepatotoxic, and genotoxic effects, in humans due to their complex structural formation during the degradation/acetylation reaction. In addition, improper preharvest, harvest, and postharvest handling tend to lead to the formation of OTA and DON in various food commodities, which allows different harmful fungicides in practice. Therefore, this review provides more insight into the distribution and toxicity of OTA/DON in the food matrix and human health. Furthermore, the interactive effects of OTA/DON with co-contaminated organic and inorganic compounds are discussed. Finally, international regulation and mitigation strategies for detoxication are critically evaluated to meet food safety and good agriculture practices.

Factors That Affect the Microbiological Stability of Chicha Morada during Its Production on an Industrial Scale: A Review

ABSTRACT

Chicha morada, also known as purple corn drink (PCD), is a traditional noncarbonated beverage commonly prepared at homes and restaurants in Peru. However, in recent years, it is being produced at an industrial scale aiming to extend its shelf life, expand its marketing, and make it known worldwide. Traditionally, this beverage, whose main component is purple corn (Zea mays L.), was made and consumed quickly and in some cases, stored under refrigeration until consumption, but never beyond 24 to 48 h. With its industrialization, factories are presented with challenges to design and provide adequate protection of the beverage, assuring its quality and safety. Although its production at an industrial level is similar to that of other noncarbonated drinks containing fruit juice, several processing factors could affect the microbiological stability desired for this beverage, such as the storage of the purple corn drink extract. In this document, a critical review of the production process (raw materials, production stages, and forms of commercialization) that can directly affect the contamination of the beverage is made. Recommendations are made for improving the control points in the industrial process and to avoid potential microbiological problems.

HIGHLIGHTS

Aflatoxin contamination in maize: occurrence and health implications in Latin America

According to the United Nations Food and Agriculture Organisation, mycotoxicoses constitute the second most pressing food safety problem worldwide, with most cases occurring in developing countries. Maize (Zea mays L.), the main staple for many Latin Americans, is one of the best suitable substrates for mycotoxigenic Aspergillus fungi. Aflatoxins (AFs) produced primarily by Aspergillus flavus, are of significant concern, especially in developing countries. While AFs production occurs mainly in warmer, tropical, and subtropical environments, recent evidence suggests that global climate change favours their presence in regions with little or no awareness of this issue. AFs interfere with metabolic processes, causing cancer and other health disorders resulting in health hazards and even death. The setting of national acceptable regulatory levels of AFs is necessary for Latin American countries. Unfortunately, no estimates of the economic impact of AFs in this region are currently available nor the cost of regulatory programs designed to reduce health risks to animals and humans. This review explores relevant data about incidence of AFs in maize produced in the region and the adverse effects of the consumption of contaminated foods and the associated health consequences for Latin American consumers. Regulations aimed to mitigate AFs exposure to consumers are also reviewed and identified gaps for researchers and actors of the maize value chain are also proposed.

Occurrence of Chemical Contaminants in Peruvian Produce: A Food-Safety Perspective

The presence of chemical contaminants in agricultural products is a continued food-safety challenge in Peru. This country has robust agriculture potential, but its output of fruits and vegetables is severely impacted by massive mining activities, as well as poor farming practices, including the use of polluted irrigation water, misuse of pesticides, and inadequate postharvest conditions. This review examines the current scientific knowledge on the levels of pesticide residues, heavy metals, and mycotoxins on crops produced in Peru. The available data shows that several crop varieties are contaminated with these classes of chemical contaminants, and at levels that exceed the national and international permissible limits. The abundance of chemical contaminants in produce indicates a relevant food-safety issue, which increases the risks of chronic human diseases, like cancer—a leading cause of death in Peru. Finally, this review presents recommendations to address these contamination problems in produce grown in the Andean country.

Natural Occurrence of Mycotoxin-Producing Fusaria in Market-Bought Peruvian Cereals: A Food Safety Threat for Andean Populations

Consumption of cereals contaminated by mycotoxins poses health risks. For instance, Fumonisins B, mainly produced by Fusarium verticillioides and Fusariumproliferatum, and the type B trichothecene deoxynivalenol, typically produced by Fusarium graminearum, are highly prevalent on cereal grains that are staples of many cultural diets and known to represent a toxic risk hazard. In Peru, corn and other cereals are frequently consumed on a daily basis under various forms, the majority of food grains being sold through traditional markets for direct consumption. Here, we surveyed mycotoxin contents of market-bought grain samples in order to assess the threat these mycotoxins might represent to Peruvian population, with a focus on corn. We found that nearly one sample of Peruvian corn out of six was contaminated with very high levels of Fumonisins, levels mostly ascribed to the presence of F. verticillioides. Extensive profiling of Peruvian corn kernels for fungal contaminants could provide elements to refine the potential risk associated with Fusarium toxins and help define adapted food safety standards.