Gynostemma pentaphyllum an important medicinal herb, can absorb high amounts of cadmium (Cd) which can lead to excessive Cd contamination during the production of medicines and tea. Hence, it is crucial to investigate the response mechanism of G. pentaphyllum under Cd stress to develop varieties with low Cd accumulation and high tolerance. Physiological response analysis, transcriptomics and metabolomics were performed on G. pentaphyllum seedlings exposed to Cd stress. Herein, G. pentaphyllum seedlings could significantly enhance antioxidant enzyme activities (POD, CAT and APX), proline and polysaccharide content subject to Cd stress. Transcriptomics analysis identified the secondary metabolites, carbohydrate metabolism, amino acid metabolism, lipid metabolism, and signal transduction pathways associated with Cd stress, which mainly involved the XTH, EXP and GST genes. Metabolomics analysis identified 126 differentially expressed metabolites, including citric acid, flavonoid and amino acids metabolites, which were accumulated under Cd stress. Multi-omics integrative analysis unraveled that the phenylpropanoid biosynthesis, starch, and sucrose metabolism, alpha-linolenic acid metabolism, and ABC transporter were significantly enriched at the gene and metabolic levels in response to Cd stress in G. pentaphyllum. In conclusion, the genetic regulatory network sheds light on Cd response mechanisms in G. pentaphyllum.

Rhizobia are soil bacteria that can establish a nitrogen-fixing symbiosis with legume plants. As horizontally transmitted symbionts, the life cycle of rhizobia includes a free-living phase in the soil and a plant-associated symbiotic phase. Throughout this life cycle, rhizobia are exposed to a myriad of other microorganisms that interact with them, modulating their fitness and symbiotic performance. In this review, we describe the diversity of interactions between rhizobia and other microorganisms that can occur in the rhizosphere, during the initiation of nodulation, and within nodules. Some of these rhizobia-microbe interactions are indirect, and occur when the presence of some microbes modifies plant physiology in a way that feeds back on rhizobial fitness. We further describe how these interactions can impose significant selective pressures on rhizobia and modify their evolutionary trajectories. More extensive investigations on the eco-evolutionary dynamics of rhizobia in complex biotic environments will likely reveal fascinating new aspects of this well-studied symbiotic interaction and provide critical knowledge for future agronomical applications.

Anthocyanin is the main component of pigment in red-fleshed kiwifruit. ‘Jinhongguan’ is a new cultivar of Actinidia arguta with red peel and flesh after harvest. However, the specific types of anthocyanin in the ‘Jinhongguan’ fruit and its biosynthesis pathways remain largely unknown. Here, the total anthocyanin content in the fruit color conversion process was determined. The results showed that total anthocyanin content increased with the deepening color of the peel and flesh. To identify the genes related to anthocyanin biosynthesis and the types of anthocyanins in the ‘Jinhongguan’ fruit, a combined analysis of transcriptome and anthocyanin-targeted metabolome was carried out. A total of 5751 common differentially expressed genes (DEGs) at different stages of peel and flesh were identified, of which 2767 were common up-DEGs and 2976 were common down-DEGs. KEGG and GO enrichment analyses showed that the common up-DEGs were significantly enriched in anthocyanin synthesis-related pathways, suggesting some up-DEGs are involved in anthocyanin biosynthesis. In total, 29 metabolites were detected in the flesh by anthocyanin-targeted metabolome. Among these, nine were differential accumulation metabolites (DAMs) in comparison to red flesh vs green flesh. Six DAMs were up-regulated, with five of them were cyanidins. The content of cyanidin-3-O-galactoside was much higher than that of other DAMs, making it the main pigment in ‘Jinhongguan’. Moreover, a total of 36 anthocyanin synthesis-related structural genes, 27 MYB transcription factors (TFs), 37 bHLH TFs and 9 WDR TFs were screened from the common DEGs. Correlation analysis of transcriptome and metabolome revealed that 9 structural genes, 6 MYB TFs, 6 bHLH TFs and 1 WDR TF were significantly associated with cyanidin-3-O-galactoside. Further, qRT-PCR analysis demonstrated that structural genes (AaPAL3, Aa4CL3, AaCHS2/3/8/9/11, AaDFR1/2, AaANR1, UFGT3a and UFGT6b) and TFs (MYB108, bHLH30, bHLH94-1 and WD43) play important roles in cyanidin biosynthesis. Overall, this study identified cyanidin-3-O-galactoside as the main anthocyanin type and revealed key candidate genes of red coloration of post-harvest fruit in Actinidia arguta. These findings provided new insights into the color formation mechanism of post-harvest fruit and offered a theoretical basis for color regulation in kiwifruit.

Developing novel white Guinea yam (Dioscorea rotundata) varieties is constrained by the sparse, erratic, and irregular flowering behavior of most genotypes. We tested the effectiveness of nine agronomic and hormonal treatments to enhance flowering on D. rotundata under field conditions. Genotypes responded differently to flower-inducing treatments (p<0.001). Of the test treatments, pruning and silver thiosulfate (STS) were effective in increasing the number of spikes per plant and the flowering intensity on both sparse flowering and monoecious cultivars. STS and tuber removal treatments promoted female flowers on the monoecious variety while pruning and most treatments involving pruning favored male flowers. None of the treatments induced flowering on Danacha, a non-flowering yam landrace. Flower-enhancing treatments had no significant effect on flower fertility translated by the fruit set, since most treatments recorded fruit sets above the species’ average crossability rate. Flower-enhancing techniques significantly influenced number of tubers per plant (p = 0.024) and tuber dry matter content (DMC, p = 0.0018) but did not significantly affect plant tuber yield. Nevertheless, treatments that could enhance substantially flowering intensity, such as pruning and STS, reduced tuber yield. DMC had negative associations with all flowering-related traits. This study provided insights into white yam flower induction and suggests promising treatments that can be optimized and used routinely to increase flowering in yam crop, without significantly affecting flower fertility and tuber yield.

The adoption of dicamba-tolerant (DT) soybean in the United States resulted in extensive off-target dicamba damage to non-DT vegetation across soybean-producing states. Although soybeans are highly sensitive to dicamba, the intensity of observed symptoms and yield losses are affected by the genetic background of genotypes. Thus, the objective of this study was to detect novel marker-trait associations and expand on previously identified genomic regions related to soybean response to off-target dicamba. A total of 551 non-DT advanced breeding lines derived from 232 unique bi-parental populations were phenotyped for off-target dicamba across nine environments for three years. Breeding lines were genotyped using the Illumina Infinium BARCSoySNP6K BeadChip. Filtered SNPs were included as predictors in Random Forest (RF) and Support Vector Machine (SVM) models in a forward stepwise selection loop to identify the combination of SNPs yielding the highest classification accuracy. Both RF and SVM models yielded high classification accuracies (0.76 and 0.79, respectively) with minor extreme misclassifications (observed tolerant predicted as susceptible, and vice-versa). Eight genomic regions associated with off-target dicamba tolerance were identified on chromosomes 6 [Linkage Group (LG) C2], 8 (LG A2), 9 (LG K), 10 (LG O), and 19 (LG L). Although the genetic architecture of tolerance is complex, high classification accuracies were obtained when including the major effect SNP identified on chromosome 6 as the sole predictor. In addition, candidate genes with annotated functions associated with phases II (conjugation of hydroxylated herbicides to endogenous sugar molecules) and III (transportation of herbicide conjugates into the vacuole) of herbicide detoxification in plants were co-localized with significant markers within each genomic region. Genomic prediction models, as reported in this study, can greatly facilitate the identification of genotypes with superior tolerance to off-target dicamba.

Modern sugarcane cultivars (Saccharum spp., 2n = 100~120) are complex polyploids primarily derived from interspecific hybridization between S. officinarum and S. spontaneum. Nobilization is the theory of utilizing wild germplasm in sugarcane breeding, and is the foundation for utilizing S. spontaneum for stress resistance. However, the exact chromosomal transmission remains elusive due to a lack of chromosome-specific markers. Here, we applied chromosome-specific oligonucleotide (oligo)-based probes for identifying chromosomes 1-10 of the F₁ hybrids between S. officinarum and S. spontaneum. Then, S. spontaneum-specific repetitive DNA probes were used to distinguish S. spontaneum in these hybrids. This oligo- fluorescence in situ hybridization (FISH) system proved to be an efficient tool for revealing individual chromosomal inheritance during nobilization. We discovered the complete doubling of S. officinarum-derived chromosomes in most F₁ hybrids. Notably, we also found defective S. officinarum-derived chromosome doubling in the F₁ hybrid Yacheng75-4191, which exhibited 1.5n transmission for all nonhomologous chromosomes. Altogether, these results highlight the presence of variable chromosome transmission in nobilization between S. officinarum and S. spontaneum, including 1.5n + n and 2n + n. These findings provide robust chromosome markers for in-depth studies into the molecular mechanism underlying chromosome doubling during the nobilization, as well as tracing chromosomal inheritance for sugarcane breeding.

In this work, we studied castor-oil plant Ricinus communis as a classical system for endosperm reserve breakdown. The seeds of castor beans consist of a centrally located embryo with the two thin cotyledons surrounded by the endosperm. The endosperm functions as major storage tissue and is packed with nutritional reserves, such as oil, proteins, and starch. Upon germination, mobilization of the storage reserves requires inter-organellar interplay of plastids, mitochondria, and peroxisomes to optimize growth for the developing seedling. To understand their metabolic interactions, we performed a large-scale organellar proteomic study on castor bean endosperm. Organelles from endosperm of etiolated seedlings were isolated and subjected to liquid chromatography-tandem mass spectrometry (LC-MS/MS). Computer-assisted deconvolution algorithms were applied to reliably assign the identified proteins to their correct subcellular localization and to determine the abundance of the different organelles in the heterogeneous protein samples. The data obtained were used to build a comprehensive metabolic model for plastids, mitochondria, and peroxisomes during storage reserve mobilization in castor bean endosperm.

Syzygium is a large and diverse tree genus in the Myrtaceae family. Genome assemblies for clove (Syzygium aromaticum, 370 Mb) and sea apple (Syzygium grande, 405 Mb) provided the first insights into the genomic features and evolution of the Syzygium genus. Here, we present additional de novo chromosome-scale genome assemblies for Syzygium malaccense, Syzygium aqueum, Syzygium jambos, and Syzygium syzygioides. Genome profiling analyses show that S. malaccense, like S. aromaticum and S. grande, is diploid (2n = 2x = 22), while the S. aqueum, S. jambos, and S. syzygioides specimens are autotetraploid (2n = 4x = 44). The genome assemblies of S. malaccense (430 Mb), S. aqueum (392 Mb), S. jambos (426 Mb), and S. syzygioides (431 Mb) are highly complete (BUSCO scores of 98%). Comparative genomics analyses showed conserved organization of the 11 chromosomes with S. aromaticum and S. grande, and revealed species-specific evolutionary dynamics of the long terminal repeat retrotransposon elements belonging to the Gypsy and Copia lineages. This set of Syzygium genomes is a valuable resource for future structural and functional comparative genomic studies on Myrtaceae species.