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Summary The rubber tree (Hevea brasiliensis) is grown in tropical regions and is the major source of natural rubber. Using traditional breeding approaches, the latex yield has increased by sixfold in the last century. However, the underlying genetic basis of rubber yield improvement is largely unknown. Here, we present a high‐quality, chromosome‐level genome sequence of the wild rubber tree, the first report on selection signatures and a genome‐wide association study (GWAS) of its yield traits. Population genomic analysis revealed a moderate population divergence between the Wickham clones and wild accessions. Interestingly, it is suggestive that H. brasiliensis and six relatives of the Hevea genus might belong to the same species. The selective sweep analysis found 361 obvious signatures in the domesticated clones associated with 245 genes. In a 15‐year field trial, GWAS identified 155 marker–trait associations with latex yield, in which 326 candidate genes were found. Notably, six genes related to sugar transport and metabolism, and four genes related to ethylene biosynthesis and signalling are associated with latex yield. The homozygote frequencies of the causal nonsynonymous SNPs have been greatly increased under selection, which may have contributed to the fast latex yield improvement during the short domestication history. Our study provides insights into the genetic basis of the latex yield trait and has implications for genomic‐assisted breeding by offering valuable resources in this new domesticated crop.

Rubber tree ( Hevea brasiliensis ) is the primary source of natural rubber and economically important. We present the haplotype-resolved, telomere-to-telomere, gap-free genome assembly of the cultivar CATAS 7-33–97, with both haplotypes containing complete telomeric and centromeric regions. Structural variations, including a 32.71 Mb inversion on chromosome 8, are identified. The fully assembled 36 chromosomes enable comprehensive identification of rubber biosynthesis genes and their allele-specific expression. By integrating transcriptomic and metabolomic data, we reconstruct the rubber biosynthesis pathway and confirm the mevalonate (MVA) pathway as the major carbon source for rapid latex regeneration during tapping. Jasmonic acid (JA) plays a key role in promoting rubber yield by enhancing biosynthetic activity in response to mechanical wounding. We propose a model where JA-induced myelocytomatosis proteins 2 activate mevalonate kinase 1 expression, boosting MVA synthesis and rubber production. These findings provide insights into rubber tree genomics and its molecular response to tapping. Authors report the assembly of the haplotype-resolved and telomere-to-telomere genome of a key rubber tree variety and uncover major structural variations. It is also revealed that jasmonic acid enhances rubber yield by activating the mevalonate pathway during tapping.

Cytochrome P450 monooxygenases (CYPs) are crucial in plant secondary metabolism, catalyzing diverse biochemical reactions, defense, and stress adaptation. Hevea brasiliensis is the primary source of natural rubber, but its CYP family remains underexplored, which may play essential roles in rubber biosynthesis and environmental tolerance. n this study, we systematically identified 238 HbCYP genes in H. brasiliensis, classified them into 9 clans and 43 subfamilies, with Clan 71 contraction and Clan 72 and Clan 85 emerging as the most expansive clans. Gene structure analysis revealed that 68.87% of A-type HbCYPs have one intron. Separately, analysis of conserved motifs in promoter regions identified a high abundance of cis-acting elements, including 456 related to methyl jasmonate (meJA) responsiveness and 3,302 related to light responsiveness. Genome evolution analysis indicated that 64 tandem and 119 WGD or segmental duplications significantly contributed to the expansion of the HbCYP family, also supported by orthologous genes with other four species. Tissue-specific profiling revealed differential HbCYPs expression across H. brasiliensis organs. Notably, meJA and ethylene (ET) treatments differentially expressed 93 and 60 HbCYP genes, respectively. Gene Ontology (GO) analysis and real-time quantitative polymerase chain reaction (RT-qPCR) validation of these genes revealed their significant contribution in rubber biosynthetic pathways. Protein interaction networks highlighted collaborations between HbCYPs and key rubber biosynthesis enzymes, including 3-hydroxy-3-methylglutaryl-CoA synthase (HMGS), and these results demonstrate functional diversification within the HbCYP family associated with rubber biosynthesis. Collectively, this study provides the first comprehensive genome-wide analysis of the HbCYP family in H. brasiliensis, offering insights into their evolutionary dynamics and functional diversification. The results establish a foundation for future research on CYP-mediated rubber biosynthesis and stress adaptation, with implications for molecular breeding of high-yield and stress-tolerant rubber tree cultivars.

Lesion mimic mutants display spontaneous cell death, and thus are valuable for understanding the molecular mechanism of cell death and disease resistance. Although a lot of such mutants have been characterized in rice, the relationship between lesion formation and abscisic acid (ABA) synthesis pathway is not reported. In the present study, we identified a rice mutant, ( ), exhibiting spontaneous cell death, pre-harvest sprouting, enhanced growth, and resistance to rice bacterial and blast diseases. Cell death in the mutant was accompanied with excessive accumulation of H O . Enhanced disease resistance was associated with cell death and upregulation of defense-related genes. Map-based cloning identified a G-to-A point mutation resulting in a D-to-N substitution at the amino acid position 110 of OsABA2 (LOC_Os03g59610) in . Knock-out of through CRISPR/Cas9 led to phenotypes similar to those of . Consistent with the function of in ABA biosynthesis, ABA level in the mutant was significantly reduced. Moreover, exogenous application of ABA could rescue all the mutant phenotypes of . Taken together, our data linked ABA deficiency to cell death and provided insight into the role of ABA in rice disease resistance.

Background Panicle is a harvesting organ of rice, and its morphology and development are closely associated with grain yield. The current study was carried on a mutant screened through an EMS (ethyl-methane sulphonate) mutagenized population of a Japonica cultivar Kitaake (WT ) . Results A mutant, named as asp-lsl ( aberrant spikelet-long sterile lemma ), showed a significant decrease in plant height, number of tillers, thousand-grains weight, seed setting rate, spikelet length, kernel length and effective number of grains per panicle as compared to WT. Asp-lsl showed a pleiotropic phenotype coupled with the obvious presence of a long sterile lemma. Cross-sections of lemma showed an increase in the cell volume rather than the number of cells. Genetic segregation analysis revealed its phenotypic trait is controlled by a single recessive nuclear gene. Primary and fine mapping indicated that candidate gene controlling the phenotype of asp-lsl was located in an interval of 212 kb on the short arm of chromosome 8 between RM22445 and RM22453. Further sequencing and indels markers analysis revealed LOC_Os08g06480 harbors a single base substitution (G→A), resulting in a change of 521st amino acid(Gly→Glu. The homology comparison and phylogenetic tree analysis revealed mutation was occurred in a highly conserved domain and had a high degree of similarity in Arabidopsis, corn, and sorghum. The CRISPR/Cas9 mutant line of ASP-LSL produced a similar phenotype as that of asp-lsl . Subcellular localization of ASP-LSL revealed that its protein is localized in the nucleus. Relative expression analysis revealed ASP-LSL was preferentially expressed in panicle, stem, and leaves. The endogenous contents of GA, CTK, and IAA were found significantly decreased in asp-lsl as compared to WT. Conclusions Current study presents the novel phenotype of asp-lsl and also validate the previously reported function of OsREL2 (ROMOSA ENHANCER LOCI2) , / ASP1(ABERRANT SPIKELET AND PANICLE 1).

Panicle apical abortion (PAA) causes severe yield losses in rice production, but details about its development and molecular basis remain elusive. Herein, a PAA mutant, , was identified among the progeny of an elite indica maintainer rice line Yixiang 1B (YXB) mutagenized population obtained using ethyl methyl sulfonate. The abortion rate of spikelets in was observed up to 60%. Genetic mapping combined with Mutmap analysis revealed that harbored a single-bp substitution (C to T) that altered its transcript length. This gene encodes calcineurin B-like protein-interacting protein kinase 31 (OsCIPK31) localized into the cytoplasm, and is preferentially expressed in transport tissues of rice. Complementation of by transferring the open reading frame of from YXB reversed the mutant phenotype, and conversely, gene editing by knocking out of in YXB results in PAA phenotype. Our results support that plays an important role in panicle development. We found that dysregulation is caused by the disruption of function due to excessive accumulation of ROS, which ultimately leads to cell death in rice panicle. and MAPK pathway might have a synergistic effect to lead ROS accumulation in response to stresses. Meanwhile the PAA distribution is related to IAA hormone accumulation in the panicle. Our study provides an understanding of the role of OsCIPK31 in panicle development by responding to various stresses and phytohormones.

Background Polyploidy, or whole-genome duplication (WGD) promotes genetic diversification in plants. However, whether WGD is accompanied by epigenetic regulation especially DNA methylation remains yet elusive. Methylation of different region in genomic DNA play discrete role in gene regulation and developmental processes in plants. Results In our study, we used an apomictic rice line (SARII-628) that produces twin seedlings of different ploidy for methylated DNA immunoprecipitation sequencing (MeDIP-seq). We compared the level of methylation and mRNA expression in three different (CG, CHG, and CHH) sequence contexts of promoter region among haploid (1X), diploid (2X), and triploid (3X) seedling. We used MeDIP-Seq analysis of 14 genes to investigate whole genome DNA methylation and found that relative level of DNA methylation across different ploidy was in following order e.g. diploid > triploid > haploid. GO functional classification of differentially methylated genes into 9 comparisons group of promoter, intergenic and intragenic region discovered, these genes were mostly enriched for cellular component, molecular function, and biological process. By the comparison of methylome data, digital gene expression (DGE), mRNA expression profile, and Q-PCR findings LOC_ Os07g31450 and LOC_ Os01g59320 were analyzed for BS-Seq (Bisulphite sequencing). Conclusions We found that (1) The level of the promoter DNA methylation is negatively correlated with gene expression within each ploidy level. (2) Among all ploidy levels, CG sequence context had highest methylation frequency, and demonstrated that the high CG methylation did reduce gene expression change suggesting that DNA methylation exert repressive function and ensure genome stability during WGD. (3) Alteration in ploidy (from diploid to haploid, or diploid to triploid) reveals supreme changes in methylation frequency of CHH sequence context. Our finding will contribute an understanding towards lower stability of CHH sequence context and educate the effect of promoter region methylation during change in ploidy state in rice.

The Gibberellic Acid Stimulated in Arabidopsis (GASA) gene family is regulated by gibberellins and plays a crucial role in regulating plant growth and development. Based on rubber tree genome data, 18 HbGASA genes, designated HbGASA1 to HbGASA18, were identified in Hevea brasiliensis. Comprehensive bioinformatics analyses were performed to characterize gene structures, chromosomal distributions, syntenic relationships, protein architectures, phylogenetic evolution, and expression profiles. The expression patterns of HbGASA genes under low-temperature stress were further validated by quantitative real-time polymerase chain reactions (qRT-PCR). The results demonstrated that the 18 HbGASA genes were unevenly distributed across 10 chromosomes. The encoded proteins ranged from 88 to 253 amino acids in length, and the number of exons varied from 2 to 4. Phylogenetic analysis clustered these genes into three distinct clades. Conserved motif analysis identified 10 conserved motifs, with Motif 1 and Motif 2 being highly conserved across all members. Promoter analysis revealed multiple hormone-responsive and stress-related regulatory cis-acting elements. Transcripts of the 18 HbGASA genes were detected in various tissues, and significant differences were observed in their expression levels. Under cold stress, qRT-PCR results showed that multiple HbGASA genes were significantly up-regulated. This study provides valuable insights into the structure, evolution, and functional diversification of GASA genes in the important tropical crop, H. brasiliensis.

Chilling stress is considered the major abiotic stress affecting the growth, development, and yield of rice. To understand the transcriptomic responses and methylation regulation of rice in response to chilling stress, we analyzed a cold-tolerant variety of rice (Oryza sativa L. cv. P427). The physiological properties, transcriptome, and methylation of cold-tolerant P427 seedlings under low-temperature stress (2–3 °C) were investigated. We found that P427 exhibited enhanced tolerance to low temperature, likely via increasing antioxidant enzyme activity and promoting the accumulation of abscisic acid (ABA). The Methylated DNA Immunoprecipitation Sequencing (MeDIP-seq) data showed that the number of methylation-altered genes was highest in P427 (5496) and slightly lower in Nipponbare (Nip) and 9311 (4528 and 3341, respectively), and only 2.7% (292) of methylation genes were detected as common differentially methylated genes (DMGs) related to cold tolerance in the three varieties. Transcriptome analyses revealed that 1654 genes had specifically altered expression in P427 under cold stress. These genes mainly belonged to transcription factor families, such as Myeloblastosis (MYB), APETALA2/ethylene-responsive element binding proteins (AP2-EREBP), NAM-ATAF-CUC (NAC) and WRKY. Fifty-one genes showed simultaneous methylation and expression level changes. Quantitative RT-PCR (qRT-PCR) results showed that genes involved in the ICE (inducer of CBF expression)-CBF (C-repeat binding factor)—COR (cold-regulated) pathway were highly expressed under cold stress, including the WRKY genes. The homologous gene Os03g0610900 of the open stomatal 1 (OST1) in rice was obtained by evolutionary tree analysis. Methylation in Os03g0610900 gene promoter region decreased, and the expression level of Os03g0610900 increased, suggesting that cold stress may lead to demethylation and increased gene expression of Os03g0610900. The ICE-CBF-COR pathway plays a vital role in the cold tolerance of the rice cultivar P427. Overall, this study demonstrates the differences in methylation and gene expression levels of P427 in response to low-temperature stress, providing a foundation for further investigations of the relationship between environmental stress, DNA methylation, and gene expression in rice.