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Serotonin (5-hydroxytryptamine) is an essential neurotransmitter involved in regulating various behaviors in plant-parasitic nematodes, including locomotion, egg laying, feeding, and mating. However, the functional role of serotonin in root-knot nematode invasion of host plants and the molecular mechanisms underlying feeding behavior remain poorly understood. In this study, we tested the effects of exogenous serotonin and the pharmacological compounds fluoxetine and methiothepin on the feeding behaviors of Meloidogyne graminicola . Our results suggested that M. graminicola possesses an endogenous serotonin signaling pathway and that serotonin plays a crucial role in modulating feeding behaviors in M. graminicola second-stage juveniles. We also identified and cloned the serotonin synthesis enzyme tryptophan hydroxylase ( Mg-tph-1 ) in M. graminicola and investigated the role of endogenous serotonin by generating RNA interference nematodes in Mg-tph-1 . Silencing Mg-tph-1 substantially reduced nematode invasion, development, and reproduction. According to the immunostaining results, we speculated that these serotonin immunoreactive cells near the nerve ring in M. graminicola are likely homologous to Caenorhabditis elegans ADFs, NSMs, and RIH serotonergic neurons. Furthermore, we investigated the impact of phytoserotonin on nematode invasion and development in rice by overexpressing OsTDC-3 or supplementing rice plants with tryptamine and found that an increase in phytoserotonin increases nematode pathogenicity. Overall, our study provides insights into the essential role of serotonin in M. graminicola host plant parasitism and proposes that the serotonergic signaling pathway could be a potential target for controlling plant-parasitic nematodes., Competing Interests: The author(s) declare no conflict of interest.

Cytoplasmic male sterility (CMS) lines are important for breeding hybrid crops, and utilization of CMS lines requires strong fertility restorer (Rf) genes. Rf4, a major Rf for Wild-Abortive CMS (CMS-WA), has been cloned in rice. However, the Rf4 evolution and formation of CMS-WA/Rf system remain elusive. Here, we show that the Rf4 locus emerges earlier than the CMS-WA gene WA352 in wild rice, and 69 haplotypes of the Rf4 locus are generated in the Oryza genus through the copy number and sequence variations. Eight of these haplotypes of the Rf4 locus are enriched in modern rice cultivars during natural and human selections, whereas non-functional rf4i is preferentially selected for breeding current CMS-WA lines. We further verify that varieties carrying two-copy Rf4 haplotype have stronger fertility restoration ability and are widely used in three-line hybrid rice breeding. Our findings increase our understanding of CMS/Rf systems and will likely benefit crop breeding., (© 2023. The Author(s).)

Weedy rice (Oryza spp.), one of the most notorious weeds of cultivated rice, evades eradication through stem lodging and seed shattering. Many studies have focused on seed shattering, whereas variations in lodging have received less attention and the underlying mechanisms that cause the differences in lodging between weedy and cultivated rice have not been studied in detail. Here, we compared lodging variation among diverse Chinese weedy rice strains and between weedy rice and co-occurring cultivated rice. The chemical composition of basal stems was determined, and transcriptome and methylome sequencing were used to assess the variation in expression of lodging-related genes. The results showed that the degree of lodging varied between indica-derived weed strains with high lodging levels, which occurred predominantly in southern China, and japonica-derived strains with lower lodging levels, which were found primarily in the north. The more lodging-prone indica weedy rice had a smaller bending stress and lower lignin content than non-lodging accessions. In comparison to co-occurring cultivated rice, there was a lower ratio of cellulose to lignin content in the lodging-prone weedy rice. Variation in DNA methylation of lignin synthesis-related OsSWN1, OsMYBX9, OsPAL1, and Os4CL3 mediated the differences in their expression levels and affected the ratio of cellulose to lignin content. Taken together, our results show that DNA methylation in lignin-related genes regulates variations in stem strength and lodging in weedy rice, and between weed strains and co-occurring cultivated rice., (© The Author(s) 2022. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

N 6 -methyladenosine (m 6 A) modification affects the post-transcriptional regulation of eukaryotic gene expression, but the underlying mechanisms and their effects in plants remain largely unknown. Here, we report that the N 6 -adenine methyltransferase-like domain-containing protein ENHANCED DOWNY MILDEW 2-LIKE (OsEDM2L) is essential for rice (Oryza sativa L.) anther development. The osedm2l knockout mutant showed delayed tapetal programmed cell death (PCD) and defective pollen development. OsEDM2L interacts with the transcription factors basic helix-loop-helix 142 and TAPETUM DEGENERATION RETARDATION to regulate the expression of ETERNAL TAPETUM 1 (EAT1), a positive regulator of tapetal PCD. Mutation of OsEDM2L altered the transcriptomic m 6 A landscape, and caused a distinct m 6 A modification of the EAT1 transcript leading to dysregulation of its alternative splicing and polyadenylation, followed by suppression of the EAT1 target genes OsAP25 and OsAP37 for tapetal PCD. Therefore, OsEDM2L is indispensable for proper messenger RNA m 6 A modification in rice anther development., (© 2021 Institute of Botany, Chinese Academy of Sciences.)

Timely degradation of anther tapetal cells is a prerequisite for normal pollen development in flowering plants. Although several genes involved in tapetum development have been identified, the molecular basis of tapetum degeneration regulation remains poorly understood. In this study, we identified and characterized the nucleus-encoded, conserved mitochondrial aldehyde dehydrogenase OsALDH2b as a key regulator of tapetum degeneration in rice (Oryza sativa). OsALDH2b was highly expressed in anthers from meiosis to the early microspore stage. Mutation of OsALDH2b resulted in excess malonaldehyde accumulation and earlier programmed cell death in the tapetum, leading to premature tapetum degeneration and abnormal microspore development. These results demonstrate that OsALDH2b negatively regulates tapetal programmed cell death and is required for male reproductive development, providing insights into the regulation of tapetum development in plants., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology.)

Accurate quantitative reverse transcription PCR (qRT-PCR) requires reliable reference genes whose expression does not vary in different tissues and developmental stages. However, few reliable reference genes are available for qRT-PCR in rice (Oryza sativa). Here, we established an effective strategy for identifying novel reference genes (NRGs) for reliable normalization of qRT-PCR data in various rice organs and developmental stages. We selected candidate NRGs using the Information Commons for Rice Database and confirmed their expression in Rice Expression Profile Database (RiceXPro) data. Genes with low variation (<2.5 cycle quantification) across tissues and developmental stages, and little fluctuation in expression in heatmaps from RiceXPro data were considered stable NRGs. To validate this strategy, we selected 11 candidate NRGs and calculated their expression stability in different spatio-temporal conditions using five programs, and compared these genes with five established reference genes (ERGs). Only one of the ERGs (UBQ5) was reliable and 10 of the candidate NRGs were more stable than the four remaining ERGs. Therefore, public transcriptomic databases are useful for identifying NRGs. We selected two NRGs, UFC1 (Homolog of UFM1-Conjugating Enzyme 1) and FhaB (Homolog of Adhesin FhaB) for qRT-PCR analysis in rice; their homologs might be suitable for other monocot plants.