Chilling susceptibility in mungbean varieties is associated with their differentially expressed genes

Physiological and transcriptomic profiles reveal key regulatory pathways involved in cold resistance in sunflower seedlings

During sunflower growth, cold waves often occur and impede plant growth. Therefore, it is crucial to study the underlying mechanism of cold resistance in sunflowers. In this study, physiological analysis revealed that as cold stress increased, the levels of ROS, malondialdehyde, ascorbic acid, and dehydroascorbic acid and the activities of antioxidant enzymes increased. Transcriptomics further identified 10,903 DEGs between any two treatments. Clustering analysis demonstrated that the expression of MYB44a, MYB44b, MYB12, bZIP2 and bZIP4 continuously upregulated under cold stress. Cold stress can induce ROS accumulation, which interacts with hormone signals to activate cold-responsive transcription factors regulating target genes involved in antioxidant defense, secondary metabolite biosynthesis, starch and sucrose metabolism enhancement for improved cold resistance in sunflowers. Additionally, the response of sunflowers to cold stress may be independent of the CBF pathway. These findings enhance our understanding of cold stress resistance in sunflowers and provide a foundation for genetic breeding.

Comparative Analysis Highlights Uniconazole's Efficacy in Enhancing the Cold Stress Tolerance of Mung Beans by Targeting Photosynthetic Pathways

Soybean (Glycine max) and mung bean (Vigna radiata) are key legumes with global importance, but their mechanisms for coping with cold stress-a major challenge in agriculture-have not been thoroughly investigated, especially in a comparative study. This research aimed to fill this gap by examining how these two major legumes respond differently to cold stress and exploring the role of uniconazole, a potential stress mitigator. Our comprehensive approach involved transcriptomic and metabolomic analyses, revealing distinct responses between soybean and mung bean under cold stress conditions. Notably, uniconazole was found to significantly enhance cold tolerance in mung bean by upregulating genes associated with photosynthesis, while its impact on soybean was either negligible or adverse. To further understand the molecular interactions, we utilized advanced machine learning algorithms for protein structure prediction, focusing on photosynthetic pathways. This enabled us to identify LOC106780309 as a direct binding target for uniconazole, confirmed through isothermal titration calorimetry. This research establishes a new comparative approach to explore how soybean and mung bean adapt to cold stress, offers key insights to improve the hardiness of legumes against environmental challenges, and contributes to sustainable agricultural practices and food security.

Exogenous uniconazole enhances tolerance to chilling stress in mung beans (Vigna radiata L.) through cross talk among photosynthesis, antioxidant system, sucrose metabolism, and hormones

To monitor the role of exogenous uniconazole in mitigating chilling stress, this study investigated the effect of foliar spraying of 50 mg L^-1 uniconazole on the chilling (15 °C) tolerance of mung beans at the flowering stage. The results showed that uniconazole significantly enhanced the reactive oxygen species (ROS) scavenging ability of mung beans by increasing the superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), glutathione reductase (GR) activities, the contents of ascorbic acid (AsA) and glutathione (GSH), and the transcription levels of SOD and POD under chilling stress. The uniconazole applications also drastically increased the net photosynthetic rate (P_n), maximum net photosynthetic rate (P_nmax), maximum quantum yield of PSII (F_v/F_m), and the expression levels of the corresponding photosynthetic genes PsbO, PsbP, PsbQ, PsbY, and Psb28. This, in turn, resulted in a higher sucrose content. Meanwhile, uniconazole increased the indole-3-acetic acid (IAA) content but reduced the gibberellin A3 (GA₃) content under chilling stress. During the recovery period, the photosynthetic parameters and ROS of plants receiving uniconazole recovered faster, and the antioxidant activity and non-antioxidant contents were higher than in chilling-treated plants. Additionally, chilling stress markedly reduced the pod number per plant, grain number per plant, and 100-seed weight, whereas uniconazole significantly increased the grain weight per plant by 53.47% compared to the chilling treatment. These results strongly suggest that uniconazole can effectively protect mung beans from chilling stress damage by protecting the photosynthetic machinery and enhancing the antioxidant capacity to quench excessive ROS caused by chilling stress. These effects are closely relevant to chilling tolerance enhancement and yield improvement in mung beans.

Transcriptomic analysis of Vigna radiata in response to chilling stress and uniconazole application

Background

Chilling injury of mung bean (Vigna radiata (L.)) during the blooming and podding stages is a major agricultural threat in Northeast China. Uniconazole (UNZ) can alleviate water deficit stress in soybean and waterlogging stress in mung bean. However, there has been no report on the effect of UNZ application on the growth and transcriptomic profile of mung bean under chilling stress.

Results

UNZ application before chilling stress at the R1 stage alleviated the decline in mung bean yield. UNZ delayed the decrease in leaf chlorophyll content under chilling stress at the R1 stage and accelerated the increase in leaf chlorophyll content during the recovery period. Eighteen separate RNA-Seq libraries were generated from RNA samples collected from leaves exposed to six different treatment schemes. The numbers of DEGs specific for UNZ treatment between D1 + S vs. D1 and D4 + S vs. D4 were 708 and 810, respectively. GO annotations showed that photosynthesis genes were obviously enriched among the genes affected by chilling stress and UNZ application. KEGG pathway enrichment analysis indicated that 4 pathways (cutin, suberin and wax biosynthesis; photosynthesis; porphyrin and chlorophyll metabolism; and ribosome) were downregulated, while plant–pathogen interaction was upregulated, by chilling stress. UNZ application effectively prevented the further downregulation of the gene expression of members of these 4 KEGG pathways under chilling stress.

Conclusions

UNZ application effectively delayed the decrease in photosynthetic pigment content under chilling stress and accelerated the increase in photosynthetic pigment content during the recovery period, thus effectively limiting the decline in mung bean yield. UNZ application effectively prevented the further downregulation of the gene expression of members of 4 KEGG pathways under chilling stress and increased mung bean tolerance to chilling stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08443-6.

Structural characterization of plant glucosylceramides and the corresponding ceramides by UHPLC-LTQ-Orbitrap mass spectrometry

Ceramides (CERs) play a major role in skin barrier function and direct replacement of depleted skin CERs, due to skin disorder or aging, has beneficial effects in improving skin barrier function and skin hydration. Though, plants are reliable source of CERs, absence of economical and effective method of hydrolysis to convert the dominant plant sphingolipid, glucosylceramides (GlcCERs), into CERs remains a challenge. This study aims at exploring alternative GlcCERs sources and chemical method of hydrolysis into CERs for dermal application. GlcCERs isolated from lupin bean (Lupinus albus), mung bean (Vigna radiate) and naked barley (Hordium vulgare) were identified using ultra high performance liquid chromatography hyphenated with atmospheric pressure chemical ionization - high resolution tandem mass spectrometer (UHPLC/APCI-HRMS/MS) and quantified with validated automated multiple development-high performance thin layer chromatography (AMD-HPTLC) method. Plant GlcCERs were hydrolyzed into CERs with mild acid hydrolysis (0.1 N HCl) after treating them with oxidizing agent, NaIO_4, and reducing agent, NaBH₄. GlcCERs with 4,8-sphingadienine, 8-sphingenine and 4-hydroxy-8-sphingenine sphingoid bases linked with C14 to C26 α-hydroxylated fatty acids (FAs) were identified. Single GlcCER (m/z 714.5520) was dominant in lupin and mung beans while five major GlcCERs species (m/z 714.5520, m/z 742.5829, m/z 770.6144, m/z 842.6719 and m/z 844.56875) were obtained from naked barley. The GlcCERs contents of the three plants were comparable. However, lupin bean contains predominantly (> 98 %) a single GlcCER (m/z 714.5520). Considering the affordability, GlcCER content and yield, lupin bean would be the preferred alternative commercial source of GlcCERs. CER species bearing 4,8-sphingadienine and 8-sphingenine sphingoid bases attached to C14 to 24 FAs were found after mild acid hydrolysis. CER species with m/z 552.4992 was the main component in the beans while CER with m/z 608.5613 was dominant in the naked barley. However, CERs with 4-hydroxy-8-sphingenine sphingoid base were not detected in UHPLC-HRMS/MS study suggesting that the method works for mainly GlcCERs carrying dihydroxy sphingoid bases. The method is economical and effective which potentiates the commercialization of plant CERs for dermal application.

The lipid transfer protein OsLTPL159 is involved in cold tolerance at the early seedling stage in rice

Nonspecific lipid transfer proteins (nsLTPs) play critical roles in plant development and response to abiotic stresses. Here, we found that a rice lipid transfer protein, OsLTPL159, was associated with cold tolerance at the early seedling stage. Overexpression of an OsLTPL159^IL112 allele from the cold-tolerant introgression line IL112 in either the japonica variety Zhonghua17 (ZH17) or the indica variety Teqing background dramatically enhanced cold tolerance. In addition, down-regulation of the expression of OsLTPL159 in the japonica variety ZH17 by RNA interference (RNAi) significantly decreased cold tolerance. Further transcriptomic, physiological and histological analysis showed that the OsLTPL159^IL112 allele likely enhanced the cold tolerance of rice at the early seedling stage by decreasing the toxic effect of reactive oxygen species, enhancing cellulose deposition in the cell wall and promoting osmolyte accumulation, thereby maintaining the integrity of the chloroplasts. Notably, overexpression of another allele, OsLTPL159^GC2 , from the recipient parent Guichao 2 (GC2), an indica variety, did not improve cold tolerance, indicating that the variations in the OsLTPL159 coding region of GC2 might disrupt its function for cold tolerance. Further sequence comparison found that all 22 japonica varieties surveyed had an OsLTPL159 haplotype identical to IL112 and were more cold-tolerant than the surveyed indica varieties, implying that the variations in OsLTPL159 might be associated with differential cold tolerance of japonica and indica rice. Therefore, our findings suggest that the OsLTPL159 allele of japonica rice could be used to improve cold tolerance of indica rice through a molecular breeding strategy.