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Background: Postharvest quality deterioration poses a significant challenge to the commercial value of fresh lotus seeds. Low temperature storage is widely employed as the primary method for preserving postharvest lotus seeds during storage and transportation., Results: This approach effectively extends the storage life of lotus seeds, resulting in distinct physiological changes compared to room temperature storage, including a notable reduction in starch, protein, H 2 O 2 , and MDA content. Here, we conducted RNA-sequencing to generate global transcriptome profiles of postharvest lotus seeds stored under room or low temperature conditions. Principal component analysis (PCA) revealed that gene expression in postharvest lotus seeds demonstrated less variability during low temperature storage in comparison to room temperature storage. A total of 14,547 differentially expressed genes (DEGs) associated with various biological processes such as starch and sucrose metabolism, energy metabolism, and plant hormone signaling response were identified. Notably, the expression levels of DEGs involved in ABA signaling were significantly suppressed in contrast to room temperature storage. Additionally, nine weighted gene co-expression network analysis (WGCNA)-based gene molecular modules were identified, providing insights into the co-expression relationship of genes during postharvest storage., Conclusion: Our findings illuminate transcriptional differences in postharvest lotus seeds between room and low temperature storage, offering crucial insights into the molecular mechanisms of low temperature preservation in lotus seeds., (© 2024. The Author(s).)

Background: Drought stress affects plant growth and development. DREB proteins play important roles in modulating plant growth, development, and stress responses, particularly under drought stress. To study the function of DREB transcription factors (TFs), we screened key DREB-regulating TFs for drought in Lotus japonicus., Results: Forty-two DREB TFs were identified, and phylogenetic analysis of proteins from L. japonicus classified them into five subfamilies (A1, A2, A4, A5, A6). The gene motif composition of the proteins is conserved within the same subfamily. Based on the cis-acting regulatory element analysis, we identified many growth-, hormone-, and stress-responsive elements within the promoter regions of DREB. We further analyzed the expression pattern of four genes in the A2 subfamily in response to drought stress. We found that the expression of most of the LjDREB A2 subfamily genes, especially LjDREB2B, was induced by drought stress. We further generated LjDREB2B overexpression transgenic Arabidopsis plants. Under drought stress, the growth of wild-type (WT) and overexpressing LjDREB2B (OE) Arabidopsis lines was inhibited; however, OE plants showed better growth. The malondialdehyde content of LjDREB2B overexpressing lines was lower than that of the WT plants, whereas the proline content and antioxidant enzyme activities in the OE lines were significantly higher than those in the WT plants. Furthermore, after drought stress, the expression levels of AtP5CS1, AtP5CS2, AtRD29A, and AtRD29B in the OE lines were significantly higher than those in the WT plants., Conclusions: Our results facilitate further functional analysis of L. japonicus DREB. LjDREB2B overexpression improves drought tolerance in transgenic Arabidopsis. These results indicate that DREB holds great potential for the genetic improvement of drought tolerance in L. japonicus., (© 2024. The Author(s).)

Background: The APETALA2/ethylene response factor (AP2/ERF) family are important regulatory factors involved in plants' response to environmental stimuli. However, their roles in salt tolerance in Lotus corniculatus remain unclear., Results: Here, the key salt-responsive transcription factor LcERF056 was cloned and characterised. LcERF056 belonging to the B3-1 (IX) subfamily of ERFs was considerably upregulated by salt treatment. LcERF056-fused GFP was exclusively localised to nuclei. Furthermore, LcERF056- overexpression (OE) transgenic Arabidopsis and L. corniculatus lines exhibited significantly high tolerance to salt treatment compared with wild-type (WT) or RNA interference expression (RNAi) transgenic lines at the phenotypic and physiological levels. Transcriptome analysis of OE, RNAi, and WT lines showed that LcERF056 regulated the downstream genes involved in several metabolic pathways. Chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-qPCR) and yeast one-hybrid (Y1H) assay demonstrated that LcERF056 could bind to cis-element GCC box or DRE of reactive oxygen species (ROS)-related genes such as lipid-transfer protein, peroxidase and ribosomal protein., Conclusion: Our results suggested that the key regulator LcERF056 plays important roles in salt tolerance in L. corniculatus by modulating ROS-related genes. Therefore, it may be a useful target for engineering salt-tolerant L. corniculatus or other crops., (© 2021. The Author(s).)

Background: After uptake from soil into the root tissue, distribution and allocation of nitrate throughout the whole plant body, is a critical step of nitrogen use efficiency (NUE) and for modulation of plant growth in response to various environmental conditions. In legume plants nitrate distribution is also important for the regulation of the nodulation process that allows to fix atmospheric N (N 2 ) through the symbiotic interaction with rhizobia (symbiotic nitrogen fixation, SNF)., Results: Here we report the functional characterization of the Lotus japonicus gene LjNPF2.9, which is expressed mainly in the root vascular structures, a key localization for the control of nitrate allocation throughout the plant body. LjNPF2.9 expression in Xenopus laevis oocytes induces 15 NO 3 accumulation indicating that it functions as a nitrate importer. The phenotypic characterization of three independent knock out mutants indicates an increased shoot biomass in the mutant backgrounds. This phenotype is associated to an increased/decreased nitrate content detected in the shoots/roots. Furthermore, our analysis indicates that the accumulation of nitrate in the shoot does not affect the nodulation and N-Fixation capacities of the knock out mutants., Conclusions: This study shows that LjNPF2.9 plays a crucial role in the downward transport of nitrate to roots, occurring likely through a xylem-to-phloem loading-mediated activity. The increase of the shoot biomass and nitrate accumulation might represent a relevant phenotype in the perspective of an improved NUE and this is further reinforced in legume plants by the reported lack of effects on the SNF efficiency.

Background: Post-translational modification of receptor proteins is involved in activation and de-activation of signalling systems in plants. Both ubiquitination and deubiquitination have been implicated in plant interactions with pathogens and symbionts., Results: Here we present LjPUB13, a PUB-ARMADILLO repeat E3 ligase that specifically ubiquitinates the kinase domain of the Nod Factor receptor NFR5 and has a direct role in nodule organogenesis events in Lotus japonicus. Phenotypic analyses of three LORE1 retroelement insertion plant lines revealed that pub13 plants display delayed and reduced nodulation capacity and retarded growth. LjPUB13 expression is spatially regulated during symbiosis with Mesorhizobium loti, with increased levels in young developing nodules., Conclusion: LjPUB13 is an E3 ligase with a positive regulatory role during the initial stages of nodulation in L. japonicus.