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12-Oxo-phytodienoic acid reductases (OPRs) perform vital functions in plants. However, few studies have been reported in sugarcane (Saccharum spp.), and it is of great significance to systematically investigates it in sugarcane. Here, 61 ShOPRs, 32 SsOPRs, and 36 SoOPRs were identified from R570 (Saccharum spp. hybrid cultivar R570), AP85-441 (Saccharum spontaneum), and LA-purple (Saccharum officinarum), respectively. These OPRs were phylogenetically classified into four groups, with close genes similar structures. During evolution, OPR gene family was mainly expanded via whole-genome duplications/segmental events and predominantly underwent purifying selection, while sugarcane OPR genes may function differently in response to various stresses. Further, ScOPR2, a tissue-specific OPR, which was localized in cytoplasm and cell membrane and actively response to salicylic acid (SA), methyl jasmonate, and smut pathogen (Sporisorium scitamineum) stresses, was cloned from sugarcane. In addition, both its transient overexpression and stable overexpression enhanced the resistance of transgenic plants to pathogen infection, most probably through activating pathogen-associated molecular pattern/pattern-recognition receptor-triggered immunity, producing reactive oxygen species, and initiating mitogen-activated protein kinase cascade. Subsequently, the transmission of SA and hypersensitive reaction were triggered, which stimulated the transcription of defense-related genes. These findings provide insights into the function of ScOPR2 gene for disease resistance., (© 2024 Society for Experimental Biology and John Wiley & Sons Ltd.)

Key Message: Transgenic plants stably overexpressing ScOPR1 gene enhanced disease resistance by increasing the accumulation of JA, SA, and GST, as well as up-regulating the expression of genes related to signaling pathways. 12-Oxo-phytodienoate reductase (OPR) is an oxidoreductase that depends on flavin mononucleotide (FMN) and catalyzes the conversion of 12-oxophytodienoate (12-OPDA) into jasmonic acid (JA). It plays a key role in plant growth and development, and resistance to adverse stresses. In our previous study, we have obtained an OPR gene (ScOPR1, GenBank Accession Number: MG755745) from sugarcane. This gene showed positive responses to methyl jasmonate (MeJA), salicylic acid (SA), abscisic acid (ABA), and Sporisorium scitamineum, suggesting its potential for pathogen resistance. Here, in our study, we observed that Nicotiana benthamiana leaves transiently overexpressing ScOPR1 exhibited weaker disease symptoms, darker 3,3-diaminobenzidine (DAB) staining, higher accumulation of reactive oxygen species (ROS), and higher expression of hypersensitive response (HR) and SA pathway-related genes after inoculation with Ralstonia solanacearum and Fusarium solanacearum var. coeruleum. Furthermore, the transgenic N. benthamiana plants stably overexpressing the ScOPR1 gene showed enhanced resistance to pathogen infection by increasing the accumulation of JA, SA, and glutathione S-transferase (GST), as well as up-regulating genes related to HR, JA, SA, and ROS signaling pathways. Transcriptome analysis revealed that the specific differentially expressed genes (DEGs) in ScOPR1-OE were significantly enriched in hormone transduction signaling and plant-pathogen interaction pathways. Finally, a functional mechanism model of the ScOPR1 gene in response to pathogen infection was depicted. This study provides insights into the molecular mechanism of ScOPR1 and presents compelling evidence supporting its positive involvement in enhancing plant disease resistance., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Gretchen Hagen3 (GH3), one of the three major auxin-responsive gene families, is involved in hormone homeostasis in vivo by amino acid splicing with the free forms of salicylic acid (SA), jasmonic acid (JA) or indole-3-acetic acid (IAA). Until now, the functions of sugarcane GH3 (SsGH3) family genes in response to biotic stresses have been largely unknown. In this study, we performed a systematic identification of the SsGH3 gene family at the genome level and identified 41 members on 19 chromosomes in the wild sugarcane species, Saccharum spontaneum. Many of these genes were segmentally duplicated and polyploidization was the main contributor to the increased number of SsGH3 members. SsGH3 proteins can be divided into three major categories (SsGH3-I, SsGH3-II, and SsGH3-III) and most SsGH3 genes have relatively conserved exon-intron arrangements and motif compositions. Diverse cis-elements in the promoters of SsGH3 genes were predicted to be essential players in regulating SsGH3 expression patterns. Multiple transcriptome datasets demonstrated that many SsGH3 genes were responsive to biotic and abiotic stresses and possibly had important functions in the stress response. RNA sequencing and RT-qPCR analysis revealed that SsGH3 genes were differentially expressed in sugarcane tissues and under Sporisorium scitamineum stress. In addition, the SsGH3 homolog ScGH3-1 gene (GenBank accession number: OP429459) was cloned from the sugarcane cultivar (Saccharum hybrid) ROC22 and verified to encode a nuclear- and membrane-localization protein. ScGH3-1 was constitutively expressed in all tissues of sugarcane and the highest amount was observed in the stem pith. Interestingly, it was down-regulated after smut pathogen infection but up-regulated after MeJA and SA treatments. Furthermore, transiently overexpressed Nicotiana benthamiana, transduced with the ScGH3-1 gene, showed negative regulation in response to the infection of Ralstonia solanacearum and Fusarium solani var. coeruleum. Finally, a potential model for ScGH3-1-mediated regulation of resistance to pathogen infection in transgenic N. benthamiana plants was proposed. This study lays the foundation for a comprehensive understanding of the sequence characteristics, structural properties, evolutionary relationships, and expression of the GH3 gene family and thus provides a potential genetic resource for sugarcane disease-resistance breeding. [ABSTRACT FROM AUTHOR]

Allene oxide synthase (AOS), one of the key enzymes in the jasmonic acid (JA) biosynthesis pathway, has been well documented in enhancing plant adaptability to the external environment, but has not yet been reported in sugarcane (Saccharum spp.). Here, eight SsAOS and 36 SoAOS genes were identified from the genomes of sugarcane wild species S. spontaneum and sugarcane tropical species S. officinarum , respectively. The phylogenetic tree showed that AOSs from different plant species were clustered into four groups, including 13-AOS, 9-AOS, 9/13-AOS type Ⅰ, and 9/13-AOS type Ⅱ. Evolutionary analysis revealed that the AOS gene family was relatively conserved in structure, but has diverse evolutionary mechanisms in S. spontaneum and S. officinarum. Cis -regulatory elements and expression pattern analysis demonstrated that SsAOSs were involved in various defensive responses which included smut stress caused by Sporisorium scitamineum. Due to the excellent performance of SsAOS1a and SsAOS1b under S. scitamineum stress, their homologous gene ShAOS1 (GenBank Accession Number: MK674850) which encoded a non-secretory acid-stable hydrophilic 9/13-AOS protein and located at the plasma membrane was isolated from a sugarcane hybrid variety YC05-179 that was inoculated with S. scitamineum for 2 d. The transcripts of ShAOS1 were up-regulated under methyl jasmonate, salicylic acid, and abscisic acid treatments. Transient overexpression of the ShAOS1 gene in Nicotiana benthamiana could promote hydrogen peroxide accumulation and induce immune-related genes expression. Furthermore, genetic transformation and RNA-sequencing (RNA-seq) analysis showed that the stable overexpression of the ShAOS1 gene enhanced the resistance of transgenic N. benthamiana plants to Fusarium solani var. coeruleum through the modulation of lots of transcription factors and protein kinases, a series of stimulus response processes and signalling pathways. These results provide the theoretical basis and candidate target genes for sugarcane disease resistance molecular breeding. • AOS genes, a part of the JA biosynthetic pathway, were identified from Saccharum. • Functional differentiation and evolutionary mechanisms of AOS genes were performed. • AOSs positively respond to smut pathogen infection. • ShAOS1 was significantly up-regulated under biotic stress. • ShAOS1 overexpression enhanced plant disease resistance. [ABSTRACT FROM AUTHOR]