Nanopriming, an advanced seed priming technology, is highly praised for its environmental friendliness, safety, and effectiveness in promoting sustainable agriculture. Studies have shown that nanopriming can enhance seed germination by stimulating the expression of aquaporins and increasing amylase production. By applying an appropriate concentration of nanoparticles, seeds can generate reactive oxygen species (ROS), enhance their antioxidant capacity, improve their response to oxidative stress, and enhance their tolerance to both biotic and abiotic stresses. This positive impact extends beyond the seed germination and seedling growth stages, persisting throughout the entire life cycle. This review offers a comprehensive overview of recent research progress in seed priming using various nanoparticles, while also addressing current challenges and future opportunities for sustainable agriculture.

Thermoinhibition refers to the inability of seeds to germinate when inhibited by high temperatures, but when environmental conditions return to normal, the seeds are able to germinate rapidly again, which is different from thermodormancy. Meanwhile, with global warming, the effect of the thermoinhibition phenomenon on the yield and quality of crops in agricultural production is becoming common. Lettuce, as a horticultural crop sensitive to high temperature, is particularly susceptible to the effects of thermoinhibition, resulting in yield reduction. Therefore, it is crucial to elucidate the intrinsic mechanism of action of thermoinhibition in lettuce seeds. This review mainly outlines several factors affecting thermoinhibition of lettuce seed germination, including endosperm hardening, alteration of endogenous or exogenous phytohormone concentrations, action of photosensitizing pigments, production and inhibition of metabolites, maternal effects, genetic expression, and other physical and chemical factors. Finally, we also discuss the challenges and potential of lettuce seed germination thermoinhibition research. The purpose of this study is to provide theoretical support for future research on lettuce seed germination thermoinhibition, and with the aim of revealing the mechanisms and effects behind lettuce seed thermoinhibition. This will enable the identification of more methods to alleviate seed thermoinhibition or the development of superior heat-tolerant lettuce seeds.

Seed germination requires the relaxation of endosperm cap and radicle cell walls, with cell wall hydrolases playing a significant role in this process. Our study revealed that a type of cell wall hydrolase, xyloglucan endotransglucosylase, may significantly contribute to endosperm weakening during lettuce seed germination. Through bioinformatics analysis, the XTH gene family in lettuce was divided into five subfamilies localized on nine chromosomes. Notably, there were significant differences in gene structure among the members of the LsXTHs family containing 1–4 exons and 20 conserved motifs. Among these motifs, motif1, motif2, and motif3 encoded the XTH structural domain. The promoter regions of LsXTHs contained a large number of cis-acting elements responsive to various abiotic stresses, such as drought, anaerobiosis, low temperature, high temperature, and salt stress. Germination experiments showed that seeds imbibed in water and 5 μmol/L abscisic acid (ABA) were able to achieve typical germination with radicle protrusion from the endosperm cap, achieving germination of 100% and 36%, respectively. Conversely, in 0.3% sodium dichloroisocyanurate (SDIC), the swollen seeds were unable to germinate or complete atypical germination, resulting in a germination rate of 30%. Compared to the control, the mechanical strength of the endosperm cap of seeds imbibed in 0.3% SDIC for 8 h increased by 14%, indicating that SDIC may inhibit seed germination by enhancing the mechanical strength of the endosperm cap. Enzyme activity analysis revealed that during lettuce seed germination, XTH enzyme activity in the endosperm cap was significantly higher than in other tissues and increased gradually with imbibition. Transcriptome analysis of the endosperm cap detected the expression of 10 LsXTH genes. Among these, LsXTH43 exhibited the highest expression during germination and was significantly upregulated two-fold by high temperatures, suggesting a potential role in the high-temperature germination of lettuce seeds. Additionally, SDIC downregulated the expression of LsXTHs to varying degrees, with the expression of LsXTH15 reduced to only 6% of its original level. Low temperature, high temperature, drought, and salt stress all reduced the expression of most LsXTHs to different degrees; when seeds germinated under waterlogging and cadmium stress, LsXTH6, LsXTH7, LsXTH8, LsXTH32, and LsXTH33 were all upregulated to some extent.

Accurate identification of high-quality seeds is crucial for maintaining superior crop traits. Lettuce is widely consumed vegetable with diverse varieties, however, the traditionally identification methods are both time-consuming and labor-intensive. This study explores feasibility of rapid, non-destructive identification of different lettuce varieties using multispectral imaging combined with machine learning. We firstly collected seed morphological and spectral data from 15 lettuce varieties using multispectral imaging. Then we applied Support Vector Machine (SVM), Random Forest (RF), and Back-Propagation Neural Network (BP), Linear Discriminant Analysis (LDA) for variety identification. The results demonstrated that multispectral imaging combined with machine learning models, effectively distinguished different lettuce seed varieties. The LDA model based on morphological and spectral fusion feature data performed best, and the average classification accuracy was 92.7 %. In the batch validation, the LDA model achieved an accuracy of 93.2 %.This method reduces cost and improves efficiency, showing great potential for seed identification in other crops.

Plant extracellular vesicles are non-self-replicating particles released by living plant cells and delimited by a lipid bilayer. They contain a large amount of lipids, RNA, and proteins. Seed vigor plays an important role in agricultural production and preservation of germplasm resources. Extracellular vesicles with cross-species communication with bioactive molecules can resist pathogens, exhibit anti-aging properties, and perform other functions; however, its potential influence on seed vigor has not been reported. In this study, rice seeds with different germination percentages were used to extract extracellular vesicles, endogenous proteins, and RNA. Protein qualitative identification and miRNA differential analysis were performed to analyze the regulatory mechanism of extracellular vesicles on seed vigor. Results: The profiles of four miRNA families were found to be significantly different: osa-miR164, osa-miR168, osa-miR166, and osa-miR159. Protein correlation analysis predicted that extracellular vesicles might mediate the synthesis of the seed cell wall; glyoxic acid cycle and tricarboxylic acid cycle; non-specific lipid transfer; mitochondrial quality control; and other biological processes to regulate rice seed viability. In addition, cupin protein, phospholipase D, aldehyde dehydrogenase, seven heat shock proteins (especially BiP1 and BiP2), protein disulfide isomerase-like (PDI), thioredoxin, calnexin and calreticulin, glutathione transferase, and other proteins found in extracellular vesicles were closely related to seed vigor. This provides a novel direction for the study of the regulation mechanism of seed vigor.

Pogostemon cablin (patchouli) is a well-known perennial herbaceous plant for traditional Chinese medicine, and its primary bioactive compounds are patchoulol and pogostone. The biosynthesis pathway of patchouli has been well resolved early, while the biosynthesis pathway of pogostone is still not fully resolved due to the lack of terminal enzyme directly synthesizing pogostone. Here, the present study aims to predict the terminal enzyme of pogostone biosynthesis and reconstruct its most possible complete biosynthesis, through the integrated transcriptomic and metabolomic analysis. The metabolomic and transcriptomic profiles of patchouli leaf were largely different to those of root and stem. Patchoulol analogs like patchoulene and germacrene mainly accumulated in leaf, while pogostone content was much higher in root. Based on the integrated analysis of differentially expressed genes and metabolites, we reconstructed the biosynthesis pathways of patchoulol, and predicted the most likely complete biosynthesis pathway of pogostone. Besides, we identified 29 highly-expressed genes involved in pogostone biosynthesis for the neo-octoploid genome of patchouli, and most of their expression levels were strongly correlated with pogostone content. In particular, patchouli BAHD-DCR acyltransferases (BAHD-DCRs) were phylogenetically distant from but structurally similar to the other known plant BAHD acyltransferases. Most of them possessed the conservative catalysis motif HXXXD, and the catalysis center could bind to the widely recognized substrate molecules of 4-hydroxy-6-methyl-2-pyrone and 4-methylvaleryl-CoA and product molecule of pogostone. Thus, the highly-expressed BAHD-DCRs in patchouli root were proposed to be terminal enzymes directly synthesizing pogostone. The findings here provide more supporting evidence for the medical use of patchouli whole plants, and make an important step forward fully resolving the pogostone biosynthesis pathway. The identified genes involved in pogostone biosynthesis, especially BAHD-DCRs, deserve further investigation and utilization in the synthetic production of pogostone.