Chlorophyll Composition, Chlorophyll Fluorescence, and Grain Yield Change in esl Mutant Rice

Metabolomics combined with proteomics reveals phytotoxic effects of norfloxacin under drought stress on Oryza sativa

In recent decades, plants enduring abiotic stresses such as drought and chemical stresses. Currently, the mechanism of combined antibiotic and drought stress response and its impact on crop growth and food security remains poorly understood. Here, the mechanism of stress responses under the exposure of norfloxacin (NF) and drought (D) individually and in combination (DNF) were explored on rice (Oryza sativa) cultivar Hanyou73 through proteomics and metabolomic analysis. All treatments adversely affected chlorophyll fluorescence kinetics, antioxidant enzyme activities, rice grain composition and yield. The results showed that in DNF the antibiotic was accumulated 627% more than NF treatment in rice grains while in leaves there was no significant difference under both treatments. The proteomic revealed that differentially expressed identified proteins were involved in carbohydrate metabolism, amino acid metabolism, photosynthesis and mRNA binding. However, the metabolomics results showed that the abundance of metabolites related to RNA biosynthesis and amino acid metabolism were more affected. The disruptions caused in rice plant under DNF treatment become more severe, this makes it more susceptible than individual D and NF treatment. These findings improve our knowledge about the response of rice plant to cope with antibiotic contamination alone and in combination with drought.

Chlorophyllase (PsCLH1) and light-harvesting chlorophyll a/b binding protein 1 (PsLhcb1) and PsLhcb5 maintain petal greenness in Paeonia suffruticosa 'Lv Mu Yin Yu'

INTRODUCTION

Green flowers are not an adaptive trait in natural plants due to the challenge for pollinators to discriminate from leaves, but they are valuable in horticulture. The molecular mechanisms of green petals remain unclear. Tree peony (Paeonia suffruticosa) is a globally cultivated ornamental plant and considered the 'King of Flowers' in China. The P. suffruticosa 'Lv Mu Yin Yu (LMYY)' cultivar with green petals could be utilized as a representative model for understanding petal-specific chlorophyll (Chl) accumulation and color formation.

OBJECTIVES

Identify the key genes related to Chl metabolism and understand the molecular mechanism of petal color changes.

METHODS

The petal color parameter was analyzed at five developmental stages using a Chroma Spectrophotometer, and Chl and anthocyanin accumulation patterns were examined. Based on comparative transcriptomes, differentially expressed genes (DEGs) were identified, among which three were functionally characterized through overexpression in tobacco plants or silencing in 'LMYY' petals.

RESULTS

During flower development and blooming, flower color changed from green to pale pink, consistent with the Chl and anthocyanin levels. The level of Chl demonstrated a similar pattern with petal epidermal cell striation density. The DEGs responsible for Chl and anthocyanin metabolism were characterized through a comparative transcriptome analysis of flower petals over three critical developmental stages. The key chlorophyllase (PsCLH1) and light-harvesting chlorophyll a/b binding protein 1 (PsLhcb1) and PsLhcb5 influenced the Chl accumulation and the greenness of 'LMYY' petals.

CONCLUSION

PsCLH1, PsLhcb1, and PsLhcb5 were critical in accumulating the Chl and maintaining the petal greenness. Flower color changes from green to pale pink were regulated by the homeostasis of Chl degradation and anthocyanin biosynthesis. This study offers insights into underlying molecular mechanisms in the green petal and a strategy for germplasm innovation.

Expression of AtNF-YB1 activates early flowering, showing potential in breeding hybrid rice

The nuclear factor Y (NF-Y) has been shown to be involved in plant growth and development in response to various environmental signals. However, the integration of these mechanisms into breeding practices for new cultivars has not been extensively investigated. In this study, the Arabidopsis gene AtNF-YB1 was introduced into rice, including inbred Kasalath and the hybrids Jinfeng × Chenghui 727 and Jinfeng × Chuanhui 907. The obtained transgenic rice showed early flowering under both natural long day (NLD) and natural short day (NSD) conditions. For the inbred Kasalath, the transgenic lines clearly showed a shorter plant height and lower grain yield, with a decrease in spike length and grain number but more productive panicles. However, the hybrids with AtNF-YB1 had much smaller or even zero reduction in spike length and grain number and more productive panicles. Thus, maintained or even increased grain yields of the transgenic hybrids were recorded under the NLD conditions. Quantitative PCR analysis indicated that the rice flowering initiation pathways were early activated via the suppression of Ghd7 induction in the transgenic rice. RNA-Seq further demonstrated that three pathways related to plant photosynthesis were markedly upregulated in both Jinfeng B and the hybrid Jinfeng × Chuanhui 907 with AtNF-YB1 expression. Moreover, physiological experiments showed an upregulation of photosynthetic rates in the transgenic lines. Taken together, this study suggests that AtNF-YB1 expression in rice not only induces early flowering but also benefits photosynthesis, which might be used to develop hybrid varieties with early ripening.

Identification of potential light deficiency response regulators in endangered species Magnolia sinostellata

Magnolia sinostellata is one of the endangered species in China and largely suffers light deficiency stress in the understory of forest. However, the weak light response molecular mechanism remains unclear. More importantly, hub genes in the molecular network have not been pinpointed. To explore potential regulators in the mechanism, weighted gene co-expression network analysis (WGCNA) was performed to analysis the trancriptome data of M. sinostellata leaves subjected to weak light with different time points. Gene co-expression analysis illustrated that module 1, 2 and 3 were closely associated with light deficiency treatment, which. Gene ontology and KEGG analyses showed that genes in module 1 mainly participated in amino and nucleotide metabolism, module 2 mostly involved in carbon fixation and module 3 mostly regulated photosynthesis related pathways, among which 6, 7 and 8 hub genes were identified, respectively. Hub genes isoform_107196 in module 1 and isoform_55976 in module 2 were unique to M. sinostellata. This study found that light deficiency inhibited photosynthesis and stress tolerance, while improved carbon metabolism and flowering related pathways in M. sinostellata, which can impact its accumulation reserves of growth and reproduction in the next season. In addition, key shade response regulators identified in this study have laid a firm foundation for further investigation of shade response molecular mechanism and protection of other shade sensitive plants.

Genome-Wide Identification of the LHC Gene Family in Kiwifruit and Regulatory Role of AcLhcb3.1/3.2 for Chlorophyll a Content

Light-harvesting chlorophyll a/b-binding (LHC) protein is a superfamily that plays a vital role in photosynthesis. However, the reported knowledge of LHCs in kiwifruit is inadequate and poorly understood. In this study, we identified 42 and 45 LHC genes in Actinidia chinensis (Ac) and A. eriantha (Ae) genomes. Phylogenetic analysis showed that the kiwifruit LHCs of both species were grouped into four subfamilies (Lhc, Lil, PsbS, and FCII). Expression profiles and qRT-PCR results revealed expression levels of LHC genes closely related to the light, temperature fluctuations, color changes during fruit ripening, and kiwifruit responses to Pseudomonas syringae pv. actinidiae (Psa). Subcellular localization analysis showed that AcLhcb1.5/3.1/3.2 were localized in the chloroplast while transient overexpression of AcLhcb3.1/3.2 in tobacco leaves confirmed a significantly increased content of chlorophyll a. Our findings provide evidence of the characters and evolution patterns of kiwifruit LHCs genes in kiwifruit and verify the AcLhcb3.1/3.2 genes controlling the chlorophyll a content.

Silicon induces metallochaperone-driven cadmium binding to the cell wall and restores redox status through elevated glutathione in Cd-stressed sugar beet

Cadmium (Cd) is toxic; however, whether silicon (Si) alleviates Cd toxicity was never studied in sugar beet. The study was conducted on 2-week-old sugar beet cultivated in the presence or absence of Cd (10 μM CdSO₄ ) and Si (1 mM Na₂ SiO₃ ) in hydroponic conditions. The morphological impairment and cellular damages observed in sugar beet upon Cd toxicity were entirely reversed due to Si. Si substantially restored the energy-providing ability, absorbed energy flux, and electron transport toward PSII, which might be correlated with the upregulation of BvIRT1 and ferric chelate reductase activity leading to the restoration of Fe status in Cd-stressed sugar beet. Although Si caused a reduction of shoot Cd, the root Cd substantially increased under Cd stress, a significant part of which was retained in the cell wall rather than in the root vacuole. While the concentration of phytochelatin and the expression of BvPCS3 (PHYTOCHELATIN SYNTHASE 3) showed no changes upon Si exposure, Si induced the expression of BvHIPP32 (HEAVY METAL-ASSOCIATED ISOPRENYLATED PLANT PROTEIN 32) in the Cd-exposed root. The BvHIPP32 and AtHIPP32 metallochaperone proteins are localized in the cell wall and they share similar sequence alignment, physiochemical properties, secondary structure, cellular localization, motif locations, domain association, and metal-binding site (cd00371) linked to the metallochaperone-like protein. It suggests that Si reduces the Cd level in shoot by retaining the excess Cd in the cell wall of roots due to the induction of BvHIPP32 gene. Also, Si stimulates glutathione-related antioxidants along with the BvGST23 expression, inferring an ascorbate-glutathione ROS detoxification pathway in Cd-exposed plants.

Variation between rice accessions in photosynthetic induction in flag leaves and underlying mechanisms

Several breeding initiatives have sought to improve flag leaf performance as its health and physiology are closely correlated to rice yield. Previous studies have described natural variation of photosynthesis for flag leaves; however, none has examined their performance under the non-steady-state conditions that prevail in crop fields. Photosynthetic induction is the transient response of photosynthesis to a change from low to high light. Rice flag leaf photosynthesis was measured in both steady- and non-steady-state conditions to characterize natural variation. Between the lowest and highest performing accession, there was a 152% difference for average CO2 assimilation during induction (Ā300), a 77% difference for average intrinsic water use efficiency during induction (iWUEavg), and a 185% difference for the speed of induction (IT50), indicating plentiful variation. No significant correlation was found between steady- and non-steady-state photosynthetic traits. Additionally, measures of neither steady-state nor non-steady-state photosynthesis of flag leaves correlated with the same measures of leaves in the vegetative growth stage, with the exception of iWUEavg. Photosynthetic induction was measured at six [CO2], to determine biochemical and diffusive limitations to photosynthesis in vivo. Photosynthetic induction in rice flag leaves was limited primarily by biochemistry.

Heating quinoa shoots results in yield loss by inhibiting fruit production and delaying maturity

Increasing global temperatures and a growing world population create the need to develop crop varieties that provide higher yields in warmer climates. There is growing interest in expanding quinoa cultivation, because of the ability of quinoa to produce nutritious grain in poor soils, with little water and at high salinity. The main limitation to expanding quinoa cultivation, however, is the susceptibility of quinoa to temperatures above approximately 32°C. This study investigates the phenotypes, genes and mechanisms that may affect quinoa seed yield at high temperatures. Using a differential heating system where only roots or only shoots were heated, quinoa yield losses were attributed to shoot heating. Plants with heated shoots lost 60-85% yield as compared with control plants. Yield losses were the result of lower fruit production, which lowered the number of seeds produced per plant. Furthermore, plants with heated shoots had delayed maturity and greater non-reproductive shoot biomass, whereas plants with both heated roots and heated shoots produced higher yields from the panicles that had escaped the heat, compared with the control. This suggests that quinoa uses a type of avoidance strategy to survive heat. Gene expression analysis identified transcription factors differentially expressed in plants with heated shoots and low yield that had been previously associated with flower development and flower opening. Interestingly, in plants with heated shoots, flowers stayed closed during the day while the control flowers were open. Although a closed flower may protect the floral structures, this could also cause yield losses by limiting pollen dispersal, which is necessary to produce fruit in the mostly female flowers of quinoa.