Genetic variation in ZmWAX2 confers maize resistance to Fusarium verticillioides

Maternal haploid induction in maize via mutation of Gamete Expression protein 1

Doubled haploid (DH) technology, based on haploid induction (HI), is a crucial tool in enhancing crop-breeding efficiency and has been successfully applied in various plant species. While many HI-related genes have been identified using diverse strategies, the genetic basis and molecular mechanisms underlying HI remain incompletely understood. In this study, we present a novel system for inducing haploid offspring through targeted mutagenesis of the Zea mays Gamete Expression protein 1 (ZmGEX1) gene in maize. Our findings reveal that zmgex1 heterozygous plants (zmgex1+/-) induce maternal haploids via self- and cross-pollination as the female parent, with an average rate of 1.34%. This indicates that the haploid progeny is exclusively maternal in origin, carrying the maternal genome. We also demonstrate that ZmGEX1 is expressed in both female spikelets and anthers, localizing to the cytoplasm, nucleus and endoplasmic reticulum. Although the transmission efficiency of the zmgex1 allele is reduced in female gametophytes, ZmGEX1 does not affect embryo sac development but influences fertilization. We propose that defective fusion of the sperm and egg nuclei may lead to haploid formation. Finally, a schematic that illustrates the potential application of the new gene ZmGEX1 in maize breeding programs is proposed. Collectively, this study identifies ZmGEX1 as a novel gene involved in maternal HI and provides a promising strategy for breeding improvements.

A plant peptide with dual activity against multidrug-resistant bacterial and fungal pathogens

Multidrug-resistant (MDR) bacteria pose a major threat to public health, and additional sources of antibacterial candidates are urgently needed. Noncanonical peptides (NCPs), derived from noncanonical small open reading frames, represent small biological molecules with important roles in biology. However, the antibacterial activity of NCPs remains largely unknown. Here, we discovered a plant-derived noncanonical antibacterial peptide (NCBP1) against both Gram-positive and Gram-negative bacteria. NCBP1 is composed of 11 amino acid residues with cationic surface potential and favorable safety and stability. Mechanistic studies revealed that NCBP1 displayed antibacterial activity by targeting phosphatidylglycerol and cardiolipin in bacterial membrane, resulting in membrane damage and dysfunction. Notably, NCBP1 showed promising efficacy in mice. Furthermore, NCBP1 effectively inhibited the growth of plant fungal pathogens and enhanced disease resistance in maize. Our results demonstrate the unexplored antimicrobial potential of plant-derived NCPs and provide an accessible source for the discovery of antimicrobial substances against MDR bacterial and fungal pathogens.

Enhancing maize resistance to Fusarium verticillioides through modulation of cell wall structure and components by ZmXYXT2

INTRODUCTION

Fusarium verticillioides (F. verticillioides) is a prevalent phytopathogen that incites severe diseases in maize, resulting in substantial reductions in grain yield and quality. Despite its widespread impact, the genetic mechanisms underlying resistance to this pathogen remain elusive, with only a limited of resistant genes having been identified to date.

OBJECTIVES

Characterize the function of ZmXYXT2 encoding a putative xylan xylosyltransferase in maize defense against F. verticillioides-induced diseases.

METHODS

Real-time quantitative PCR and transitory transformation of maize protoplasts were conducted to analyze the expression pattern and subcellular localization of ZmXYXT2. The zmxyxt2 mutant, sourced from an ethyl methanesulfonate mutagenesis library, and the ZmXYXT2-overexpressing plants, generated via Agrobacterium tumefaciens-mediated transformation, were utilized for artificial inoculation with F. verticillioides followed by disease severity assessments. Phenotypic assessments, cytological observations, analysis of cell wall components, and histochemical staining were performed to elucidate the regulatory mechanisms of ZmXYXT2.

RESULTS

The absence of ZmXYXT2 renders maize vulnerable to F. verticillioides-caused seedling blight, stalk rot, ear rot and seed rot, along with a notable increase in fumonisin B1 accumulation. Conversely, maize plants overexpressing ZmXYXT2 exhibited significantly heightened immunity to these diseases. Moreover, overexpression of ZmXYXT2 results in notable changes in the composition of maize cell walls, specifically increasing the levels of arabinose, xylose and ferulic acid. These alterations lead to cell wall thickening, effectively barring the intracellular invasion and colonization of F. verticillioides, thereby halting pathogen dissemination between cells. Intriguingly, maize plants overexpressing ZmXYXT2 exhibit enhanced stem strength without compromising yield-related traits.

CONCLUSION

ZmXYXT2 provides maize with resistance to multiple diseases triggered by F. verticillioides and mitigates the accumulation of fumonisin B1. Our study presents a novel approach to bolster maize comprehensive resistance against F. verticillioides-induced diseases by modifying cell wall composition to strengthen its natural defenses.

ZmICE1a regulates the defence-storage trade-off in maize endosperm

The endosperm of cereal grains feeds the entire world as a major food supply; however, little is known about its defence response during endosperm development. The Inducer of CBF Expression 1 (ICE1) is a well-known regulator of cold tolerance in plants. ICE1 has a monocot-specific homologue that is preferentially expressed in cereal endosperms but with an unclear regulatory function. Here we characterized the function of monocot-specific ZmICE1a, which is expressed in the entire endosperm, with a predominant expression in its peripheral regions, including the aleurone layer, subaleurone layer and basal endosperm transfer layer in maize (Zea mays). Loss of function of ZmICE1a reduced starch content and kernel weight. RNA sequencing and CUT&Tag-seq analyses revealed that ZmICE1a positively regulates genes in starch synthesis while negatively regulating genes in aleurone layer-specific defence and the synthesis of indole-3-acetic acid and jasmonic acid (JA). Exogenous indole-3-acetic acid and JA both induce the expression of numerous defence genes, which show distinct spatial-specific expression in the basal endosperm transfer layer and subaleurone layer, respectively. Moreover, we dissected a JA-ZmJAZ9-ZmICE1a-MPI signalling axis involved in JA-mediated defence regulation. Overall, our study revealed ZmICE1a as a key regulator of endosperm defence response and a coordinator of the defence-storage trade-off in endosperm development.

Genome-wide association study and molecular marker development for susceptibility to Gibberella ear rot in maize

KEY MESSAGES

Sixty-nine quantitative trait nucleotides conferring maize resistance to Gibberella ear rot were detected, including eighteen novel loci. Four candidate genes were predicted, and four kompetitive allele-specific PCR markers were developed. Maize Gibberella ear rot (GER), caused by Fusarium graminearum, is one of the most devastating diseases in maize-growing regions worldwide. Enhancing maize cultivar resistance to this disease requires a comprehensive understanding of the genetic basis of resistance to GER. In this study, 334 maize inbred lines were phenotyped for GER resistance in five environments and genotyped using the Affymetrix CGMB56K SNP Array, and a genome-wide association study of resistance to GER was performed using a 3V multi-locus random-SNP-effect mixed linear model. A total of 69 quantitative trait nucleotides (QTNs) conferring resistance to GER were detected, and all of them explained individually less than 10% of the phenotypic variation, suggesting that resistance to GER is controlled by multiple minor-effect genetic loci. A total of 348 genes located around the 200-kb genomic region of these 69 QTNs were identified, and four of them (Zm00001d029648, Zm00001d031449, Zm00001d006397, and Zm00001d053145) were considered candidate genes conferring susceptibility to GER based on gene expression patterns. Moreover, four kompetitive allele-specific PCR markers were developed based on the non-synonymous variation of these four candidate genes and validated in two genetic populations. This study provides useful genetic resources for improving resistance to GER in maize.

An insertion in the promoter of a malate dehydrogenase gene regulates malic acid content in apple fruit

Malic acid is an important flavor determinant in apple (Malus × domestica Borkh.) fruit. One known variation controlling malic acid is the A/G single nucleotide polymorphism in an aluminum-activated malate transporter gene (MdMa1). Nevertheless, there are still differences in malic acid content in apple varieties with the same Ma1 genotype (Ma1/Ma1 homozygous), such as 'Honeycrisp' (high malic acid content) and 'Qinguan' (low malic acid content), indicating that other loci may influence malic acid and fruit acidity. Here, the F1 (Filial 1) hybrid generation of 'Honeycrisp' × 'Qinguan' was used to analyze quantitative trait loci for malic acid content. A major locus (Ma7) was identified on chromosome 13. Within this locus, a malate dehydrogenase gene, MDH1 (MdMa7), was the best candidate for further study. Subcellular localization suggested that MdMa7 encodes a cytosolic protein. Overexpression and RNA interference of MdMa7 in apple fruit increased and decreased malic acid content, respectively. An insertion/deletion (indel) in the MdMa7 promoter was found to affect MdMa7 expression and malic acid content in both hybrids and other cultivated varieties. The insertion and deletion genotypes were designated as MA7 and ma7, respectively. The transcription factor MdbHLH74 was found to stimulate MdMa7 expression in the MA7 genotype but not in the ma7 genotype. Transient transformation of fruit showed that MdbHLH74 affected MdMa7 expression and malic acid content in 'Gala' (MA7/MA7) but not in 'Fuji' (ma7/ma7). Our results indicated that genetic variation in the MdMa7 (MDH1) promoter alters the binding ability of the transcription factor MdbHLH74, which alters MdMa7 (MDH1) transcription and the malic acid content in apple fruit, especially in Ma1/Ma1 homozygous accessions.

The complex relationship between disease resistance and yield in crops

In plants, growth and defence are controlled by many molecular pathways that are antagonistic to one another. This results in a 'growth-defence trade-off', where plants temporarily reduce growth in response to pests or diseases. Due to this antagonism, genetic variants that improve resistance often reduce growth and vice versa. Therefore, in natural populations, the most disease resistant individuals are often the slowest growing. In crops, slow growth may translate into a yield penalty, but resistance is essential for protecting yield in the presence of disease. Therefore, plant breeders must balance these traits to ensure optimal yield potential and yield stability. In crops, both qualitative and quantitative disease resistance are often linked with genetic variants that cause yield penalties, but this is not always the case. Furthermore, both crop yield and disease resistance are complex traits influenced by many aspects of the plant's physiology, morphology and environment, and the relationship between the molecular growth-defence trade-off and disease resistance-yield antagonism is not well-understood. In this article, we highlight research from the last 2 years on the molecular mechanistic basis of the antagonism between defence and growth. We then discuss the interaction between disease resistance and crop yield from a breeding perspective, outlining the complexity and nuances of this relationship and where research can aid practical methods for simultaneous improvement of yield potential and disease resistance.

Discovery and Development of Luvangetin from Zanthoxylum avicennae as a New Fungicide Candidate for Fusarium verticillioides

Pathogenic fungi pose a significant threat to crop yields and human healthy, and the subsequent fungicide resistance has greatly aggravated these agricultural and medical challenges. Hence, the development of new fungicides with higher efficiency and greater environmental friendliness is urgently required. In this study, luvangetin, isolated and identified from the root of Zanthoxylum avicennae, exhibited wide-spectrum antifungal activity in vivo and in vitro. Integrated omics and in vitro and in vivo transcriptional analyses revealed that luvangetin inhibited GAL4-like Zn(II)2Cys6 transcriptional factor-mediated transcription, particularly the FvFUM21-mediated FUM cluster gene expression, and decreased the biosynthesis of fumonisins inFusarium verticillioides. Moreover, luvangetin binds to the double-stranded DNA helix in vitro in the groove mode. We isolated and identified luvangetin, a natural metabolite from a traditional Chinese edible medicinal plant and uncovered its multipathogen resistance mechanism. This study is the first to reveal the mechanism underlying the antifungal activity of luvangetin and provides a promising direction for the future use of plant-derived natural products to prevent and control plant and animal pathogenic fungi.

Comparative transcriptome provides insights into gene regulation network associated with the resistance to Fusarium wilt in grafted wax gourd Benincasa hispida

Introduction

Wilt is a soil-borne disease caused by Fusarium that has become a serious threat to wax gourd production. Disease-resistant graft wax gourds are an effective treatment for Fusarium wilt. However, there are few reports on the defense mechanism of graft wax gourd against wilt diseases.

Methods

In the present study, disease and growth indices were compared between grafted and original wax gourds after infection with Fusarium. High level of disease resistance was observed in the grafted wax gourd, with a lower disease index and low impacts on growth after infection. RNA-seq was performed to identify the differentially expressed genes (DEGs) between the adjacent treatment time points in the grafted and original wax gourds, respectively. Then a comparative temporal analysis was performed and a total of 1,190 genes were identified to show different gene expression patterns between the two wax gourd groups during Fusarium infection.

Result and discussion

Here, high level of disease resistance was observed in the grafted wax gourd, with a lower disease index and low impacts on growth after infection. The DEG number was higher in grafted group than original group, and the enriched functional categories and pathways of DEGs were largely inconsistent between the two groups. These genes were enriched in multiple pathways, of which the mitogen-activated protein kinase (MAPK) signaling pathway enhanced the early defense response, and cutin, suberin, and wax biosynthesis signaling pathways enhanced surface resistance in grafted wax gourd in comparison to original group. Our study provides insights into the gene regulatory mechanisms underlying the resistance of grafted wax gourds to Fusarium wilt infection, which will facilitate the breeding and production of wilt-resistant rootstocks.