Phenotype and TMT-based quantitative proteomics analysis of Brassica napus reveals new insight into chlorophyll synthesis and chloroplast structure

Characterization of the gibberellic oxidase gene SdGA20ox1 in Sophora davidii (Franch.) skeels and interaction protein screening

Gibberellin 20-oxidases (GA20oxs) are multifunctional enzymes involved in regulating gibberellin (GA) biosynthesis and controlling plant growth. We identified and characterized the GA20ox1 gene in a plant height mutant of Sophora davidii, referred to as SdGA20ox1. This gene was expressed in root, stem, and leaf tissues of the adult S. davidii plant height mutant, with the highest expression observed in the stem. The expression of SdGA20ox1 was regulated by various exogenous hormones. Overexpression of SdGA20ox1 in Arabidopsis resulted in significant elongation of hypocotyl and root length in seedlings, earlier flowering, smaller leaves, reduced leaf chlorophyll content, lighter leaf color, a significant increase in adult plant height, and other phenotypes. Additionally, transgenic plants exhibited a substantial increase in biologically active endogenous GAs (GA1, GA3, and GA4) content, indicating that overexpression of SdGA20ox1 accelerates plant growth and development. Using a yeast two-hybrid (Y2H) screen, we identified two SdGA20ox1-interacting proteins: the ethylene receptor EIN4 (11430582) and the rbcS (11416005) protein. These interactions suggest a potential regulatory mechanism for S. davidii growth. Our findings provide new insights into the role of SdGA20ox1 and its interacting proteins in regulating the growth and development of S. davidii.

Light curve parametrization of three rice (Oryza sativa L.) cultivars based on mechanistic models

This study aimed to assess variations in leaf gas-exchange characteristics, leaf pigment contents, and some intrinsic traits of photosynthetic pigment molecules in three rice cultivars (cv. JR3015, Wufengyou3015, and Jifengyou3015) using mechanistic models. The findings revealed that chlorophyll content varied significantly among the three cultivars, but not maximum electron transport rate. JR3015 had lower chlorophyll content but the highest eigen-absorption cross-section (σik) and the lowest minimum average life-time of photosynthetic pigment molecules in the excited state (τmin). Our results suggested that the highest σik and the lowest τmin in JR3015 facilitated its electron transport rate despite its lower leaf chlorophyll content. Furthermore, compared to Jifengyou3015 and Wufengyou3015, JR3015 had the lowest photosynthetic electron-use efficiency via PSII, which contributed to its lowest maximum net photosynthetic rate. These findings are important in selecting rice cultivars based on their differences in photosynthetic capacity.

Integrative Transcriptomics and Proteomics Analysis of a Cotton Mutant yl1 with a Chlorophyll-Reduced Leaf

Leaf color mutants serve as ideal materials for studying photosynthesis, chlorophyll metabolism, and other physiological processes. Here, we identified a spontaneous yellow-leaf mutant (yl1) with chlorophyll-reduced leaves from G. hirsutum L. cv ZM24. Compare to wild type ZM24 with green leaves, yl1 exhibited patchy yellow leaves and reduced chlorophyll content. To further explore the mechanisms of the patchy yellow phenotype of the mutant plant, the transcriptomics and proteomics profiles were conducted for the mutant and wild types. A total of 9247 differentially expressed genes (DEGs) and 1368 differentially accumulated proteins (DAPs) were identified. Following gene ontology (GO) annotation and KEGG enrichment, the DEGs/DAPs were found to be significantly involved in multiple important pathways, including the obsolete oxidation-reduction process, photosynthesis, light-harvesting, the microtubule-based process, cell redox homeostasis, and the carbohydrate metabolic process. In photosynthesis and the light-harvesting pathway, a total of 39 DAPs/DEGs were identified, including 9 genes in the PSI, 7 genes in the PS II, 9 genes in the light-harvesting chlorophyll protein complex (LHC), 10 genes in the PsbP family, and 4 genes in the cytochrome b6/f complex. To validate the reliability of the omics data, GhPPD1, a DAPs in the PsbP family, was knocked down in cotton using the TRV-based VIGS system, and it was observed that the GhPPD1-silenced plants exhibited patchy yellow color, accompanied by a significant decrease in chlorophyll content. In conclusion, this study integrated transcriptomic and proteomic approaches to gain a deeper understanding of the mechanisms underlying the chlorophyll-reduced leaf phenotype.

Lanthanum promotes Solanum nigrum L. growth and phytoremediation of cadmium and lead through endocytosis: Physiological and biochemical response, heavy metal uptake and visualization

Rare earth elements (REEs) are important to enhance agricultural productivity. The utilization of phytoremediation as a green technology for addressing heavy metal (HMs) contamination in soil and wastewater has gained significant attention. In our research, we conducted indoor hydroponic experiments to examine the impacts of lanthanum (La) on the growth and enrichment capacity of Solanum nigrum L. (S. nigrum). S. nigrum was cultivated in 10 mg·L-1 of cadmium (Cd), 25 mg·L-1 of lead (Pb), and a mixture of both (5 mg·L-1 Cd + 15 mg·L-1 Pb). Additionally, S. nigrum were subjected to foliar spray or hydroponic supplementation of La(III). The treatment with La(III) significantly increased total fresh weight by 17.82 % to 42.20 %, compared to the treatment without La(III). Furthermore, La(III) facilitated the endocytosis of roots and enhanced Cd2+ flux ranging from 15.64 % to 75.99 % when compared to the treatment without La(III). Foliar and hydroponic application of La(III) resulted in an increase in the translocation factors (TF) in plants of Cd and Pb compared to treatments without La(III). These findings can offer valuable insights into the potential of La(III) to enhance the phytoremediation of soil or wastewater polluted with compounds.

Photosynthetic characteristics and genetic mapping of a new yellow leaf mutant crm1 in Brassica napus

Chlorophyll is one of the key factors for photosynthesis and plays an important role in plant growth and development. We previously isolated an EMS mutagenized rapeseed chlorophyll-reduced mutant (crm1), which had yellow leaf, reduced chlorophyll content and fewer thylakoid stacks. Here, we found that crm1 showed attenuated utilization efficiency of both light energy and CO2 but enhanced heat dissipation efficiency and greater tolerance to high-light intensity. BSA-Seq analysis identified a single nucleotide change (C to T) and (G to A) in the third exon of the BnaA01G0094500ZS and BnaC01G0116100ZS, respectively. These two genes encode the magnesium chelatase subunit I 1 (CHLI1) that catalyzes the insertion of magnesium into protoporphyrin IX, a pivotal step in chlorophyll synthesis. The mutation sites resulted in an amino acid substitution P144S and G128E within the AAA+ domain of the CHLI1 protein. Two KASP markers were developed and co-segregated with the yellow leaf phenotype in segregating F2 population. Loss of BnaA01.CHLI1 and BnaC01.CHLI1 by CRISPR/Cas9 gene editing recapitulated the mutant phenotype. BnaA01.CHLI1 and BnaC01.CHLI1 were located in chloroplast and highly expressed in the leaves. Furthermore, RNA-seq analyses revealed the expression of chlorophyll synthesis-related genes were upregulated in the crm1 mutant. These findings provide a new insight into the regulatory mechanism of chlorophyll synthesis in rapeseed and suggest a novel target for improving the photosynthetic efficiency and tolerance to high-light intensity in crops.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11032-023-01429-6.

SlSAMS1 enhances salt tolerance through regulation DNA methylation of SlGI in tomato

S-adenosylmethionine (SAM), which is synthesized from methionine and ATP catalyzed by S-adenosylmethionine synthetase (SAMS), is an important methyl donor in plants. SAMS and DNA methylation play an important role in the plant response to abiotic stresses. Previous studies have shown that SAMS improves salt tolerance in tomato plants, but it is not clear whether the DNA methylation pathway mediates SAMS-induced salt tolerance. This study confirmed that SlSAMS1-overexpressing plants exhibited improved salt tolerance. Through whole-genome bisulfite sequencing (WGBS) and transcriptome sequencing (RNA-seq) analysis, the study screened the circadian rhythm pathway and identified the gene SlGI in this pathway, which was regulated by SlSAMS1. The gene body region of SlGI, the core gene of the circadian rhythm pathway, was hypermethylated in SlSAMS1-overexpressing plants, and its expression level was significantly increased. Furthermore, the SlGI-overexpressing plants showed higher salt tolerance, less reduction in plant height and fresh weight, lower electrolyte leakage, malondialdehyde and H2O2 content, and higher antioxidant enzyme activity compared to wild type plants. Therefore, SlSAMS1-overexpressing plants regulated significant changes in CHG-type methylation sites of the SlGI gene body and its expression levels, leading to an enhanced salt tolerance of tomato plants.

Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase gene increased plant height and promoted secondary cell walls deposition in Arabidopsis

MAIN CONCLUSION

Ectopic expression of Camellia oleifera Abel. gibberellin 20-oxidase 1 caused a taller phenotype, promoted secondary cell wall deposition, leaf enlargement, and early flowering, and reduced chlorophyll and anthocyanin accumulation and seed enlargement phenotype in Arabidopsis. Plant height and secondary cell wall (SCW) deposition are important plant traits. Gibberellins (GAs) play important roles in regulating plant height and SCWs deposition. Gibberellin 20-oxidase (GA20ox) is an important enzyme involved in GA biosynthesis. In the present study, we identified a GA synthesis gene in Camellia oleifera. The total length of the CoGA20ox1 gene sequence was 1146 bp, encoding 381 amino acids. Transgenic plants with CoGA20ox1 had a taller phenotype; a seed enlargement phenotype; promoted SCWs deposition, leaf enlargement, and early flowering; and reduced chlorophyll and anthocyanin accumulation. Genetic analysis showed that the mutant ga20ox1-3 Arabidopsis partially rescued the phenotype of CoGA20ox1 overexpression plants. The results showed that CoGA20ox1 participates in the growth and development of C. oleifera. The morphological changes in CoGA20ox1 overexpressed plants provide a theoretical basis for further exploration of GA biosynthesis and analysis of the molecular mechanism in C. oleifera.

The hot science in rice research: How rice plants cope with heat stress

Global climate change has great impacts on plant growth and development, reducing crop productivity worldwide. Rice (Oryza sativa L.), one of the world's most important food crops, is susceptible to high-temperature stress from seedling stage to reproductive stage. In this review, we summarize recent advances in understanding the molecular mechanisms underlying heat stress responses in rice, including heat sensing and signalling, transcriptional regulation, transcript processing, protein translation, and post-translational regulation. We also highlight the irreversible effects of high temperature on reproduction and grain quality in rice. Finally, we discuss challenges and opportunities for future research on heat stress responses in rice.

Lead Responses and Tolerance Mechanisms of Koelreuteria paniculata: A Newly Potential Plant for Sustainable Phytoremediation of Pb-Contaminated Soil

Phytoremediation could be an alternative strategy for lead (Pb) contamination. K. paniculata has been reported as a newly potential plant for sustainable phytoremediation of Pb-contaminated soil. Physiological indexes, enrichment accumulation characteristics, Pb subcellular distribution and microstructure of K. paniculata were carefully studied at different levels of Pb stress (0-1200 mg/L). The results showed that plant growth increased up to 123.8% and 112.7%, relative to the control group when Pb stress was 200 mg/L and 400 mg/L, respectively. However, the average height and biomass of K. paniculata decrease when the Pb stress continues to increase. In all treatment groups, the accumulation of Pb in plant organs showed a trend of root > stem > leaf, and Pb accumulation reached 81.31%~86.69% in the root. Chlorophyll content and chlorophyll a/b showed a rising trend and then fell with increasing Pb stress. Catalase (CAT) and peroxidase (POD) activity showed a positive trend followed by a negative decline, while superoxide dismutase (SOD) activity significantly increased with increasing levels of Pb exposure stress. Transmission electron microscopy (TEM) showed that Pb accumulates in the inactive metabolic regions (cell walls and vesicles) in roots and stems, which may be the main mechanism for plants to reduce Pb biotoxicity. Fourier transform infrared spectroscopy (FTIR) showed that Pb stress increased the content of intracellular -OH and -COOH functional groups. Through organic acids, polysaccharides, proteins and other compounds bound to Pb, the adaptation and tolerance of K. paniculata to Pb were enhanced. K. paniculata showed good phytoremediation potential and has broad application prospects for heavy metal-contaminated soil.

Plastid development of albino viviparous propagules in the woody mangrove species of Kandelia obovata

The process of plastids developing into chloroplasts is critical for plants to survive. However, this process in woody plants is less understood. Kandelia obovata Sheue, Liu & Yong is a viviparous mangrove species; the seeds germinate on the maternal tree, and the hypocotyls continue to develop into mature propagules. We identified rare albino propagules through field observation among normal green and brown ones. Toward unveiling the propagule plastid development mechanism, albino propagule leaves only have etioplasts, low photosynthesis rates, and drastically reduced chlorophyll a/b and carotenoid contents, but with increased superoxide dismutase activities. To identify candidate genes controlling propagule plastid development, a genome-wide association study (GWAS) was performed between the albino and green propagules. Twenty-five significant single nucleotide polymorphisms (SNPs) were associated with albino propagule plastid development, the most significant SNPs being located on chromosomes 1 and 5. Significant differentially expressed genes were identified in porphyrin and chlorophyll metabolisms, carotenoid and flavonoid biosynthesis by combining transcriptome and GWAS data. In particular, KoDELLAs, encoding a transcription factor and KoCHS, encoding chalcone synthase, may be essential to regulate the albino propagules plastid development through weakened chlorophyll and flavonoid biosynthesis pathways while promoting chlorophyll degradation. Our results provide insights into genetic mechanisms regulating propagule plastid development in woody plants.

Proteomic Investigation of the Antibacterial Mechanism of Cefiderocol against Escherichia coli

This study aimed to investigate the antibacterial mechanism of cefiderocol (CFDC) using data-independent acquisition quantitative proteomics combined with cellular and molecular biological assays. Numerous differentially expressed proteins related to the production of NADH, reduced cofactor flavin adenine dinucleotide (FADH2), NADPH and reactive oxygen species (ROS), iron-sulfur cluster binding, and iron ion homeostasis were found to be upregulated by CFDC. Furthermore, parallel reaction monitoring analysis validated these results. Meanwhile, we confirmed that the levels of NADH, ROS, H2O2, and iron ions were induced by CFDC, and the sensitivity of Escherichia coli to CFDC was inhibited by the antioxidant vitamin C, N-acetyl-l-cysteine, and deferoxamine. Moreover, deferoxamine also suppressed the H2O2 stress induced by CFDC. In addition, knockout of the NADH-quinone oxidoreductase genes (nuoA, nuoC, nuoE, nuoF, nuoG, nuoJ, nuoL, nuoM) in the respiratory chain attenuated the sensitivity of E. coli to CFDC far beyond the effects of cefepime and ceftazidime; in particular, the E. coli BW25113 ΔnuoJ strain produced 60-fold increases in MIC to CFDC compared to that of the wild-type E. coli BW25113 strain. The present study revealed that CFDC exerts its antibacterial effects by inducing ROS stress by elevating the levels of NADH and iron ions in E. coli. IMPORTANCE CFDC was the first FDA-approved siderophore cephalosporin antibiotic in 2019 and is known for its Trojan horse tactics and broad antimicrobial activity against Gram-negative bacteria. However, its antibacterial mechanism is not fully understood, and whether it has an impact on in vivo iron ion homeostasis remains unknown. To comprehensively reveal the antibacterial mechanisms of CFDC, data-independent acquisition quantitative proteomics combined with cellular and molecular biological assays were performed in this study. The findings will further facilitate our understanding of the antibacterial mechanism of CFDC and may provide a theoretical foundation for controlling CFDC resistance in the future.

Transcriptome Analysis of Green and White Leaf Ornamental Kale Reveals Coloration-Related Genes and Pathways

Leaf color is a crucial agronomic trait in ornamental kale. However, the molecular mechanism regulating leaf pigmentation patterns in green and white ornamental kale is not completely understood. To address this, we performed transcriptome and pigment content analyses of green and white kale leaf tissues. A total of 5,404 and 3,605 different expressed genes (DEGs) were identified in the green vs. white leaf and the green margin vs. white center samples. Kyoto Encyclopedia of Genes and Genome (KEGG) pathway enrichment analysis showed that 24 and 15 common DEGs in two pairwise comparisons were involved in chlorophyll metabolism and carotenoid biosynthesis, respectively. Seventeen genes related to chlorophyll biosynthesis were significantly upregulated in green leaf tissue, especially chlH and por. Of the 15 carotenoid biosynthesis genes, all except CYP707A and BG1 were lower expressed in white leaf tissue. Green leaf tissue exhibited higher levels of chlorophyll and carotenoids than white leaf tissue. In addition, the DEGs involved in photosystem and chlorophyll-binding proteins had higher expression in green leaf tissue. The PSBQ, LHCB1.3, LHCB2.4, and HSP70 may be key genes of photosynthesis and chloroplast formation. These results demonstrated that green and white coloration in ornamental kale leaves was caused by the combined effects of chlorophyll and carotenoid biosynthesis, chloroplast development, as well as photosynthesis. These findings enhance our understanding of the molecular mechanisms underlying leaf color development in ornamental kale.

Study of Dimorphism Transition Mechanism of Tremella fuciformis Based on Comparative Proteomics

Tremella fuciformis is a dimorphic fungus that can undertake a reversible transition between yeast-like conidia and hyphal forms. The transformation mechanism and proteomic differences between these two forms have not been reported. Therefore, in this study, we attempted to explore the differential protein profiles of dikaryotic yeast-like conidia from fruiting bodies and mycelia (FBMds) and dikaryotic mycelia (DM) by synthetically applying high-resolution MS1-based quantitative data-independent acquisition (HRMS1-DIA) full proteomics and parallel reaction monitoring (PRM) targeted proteomics. The results showed that a total of 5687 proteins were quantified, and 2220 of them (39.01%) showed more than a two-fold change in expression. The functional analysis of the differentially expressed proteins (DEPs) confirmed that the DEPs were mainly located in the membrane and nucleus. The FBMds tended to express proteins involved in biosynthesis, metabolism, DNA replication and transcription, and DNA damage repair. At the same time, DM exhibited an increased expression of proteins involved in signal transduction mechanisms such as the mitogen-activated protein kinase (MAPK) signaling pathway and the Ras signaling pathway. Further, phosphorylation analysis confirmed the importance of the MAPK signaling pathway in T. fuciformis dimorphism, and comparative metabolism analysis demonstrated the metabolic difference between FBMds and DM. The information obtained in the present study will provide new insights into the difference between FBMds and DM and lay a foundation for further research on the dimorphism formation mechanism of T. fuciformis.

Proteome Changes Reveal the Protective Roles of Exogenous Citric Acid in Alleviating Cu Toxicity in Brassica napus L

Citric acid (CA), as an organic chelator, plays a vital role in alleviating copper (Cu) stress-mediated oxidative damage, wherein a number of molecular mechanisms alter in plants. However, it remains largely unknown how CA regulates differentially abundant proteins (DAPs) in response to Cu stress in Brassica napus L. In the present study, we aimed to investigate the proteome changes in the leaves of B. L. seedlings in response to CA-mediated alleviation of Cu stress. Exposure of 21-day-old seedlings to Cu (25 and 50 μM) and CA (1.0 mM) for 7 days exhibited a dramatic inhibition of overall growth and considerable increase in the enzymatic activities (POD, SOD, CAT). Using a label-free proteome approach, a total of 6345 proteins were identified in differentially treated leaves, from which 426 proteins were differentially expressed among the treatment groups. Gene ontology (GO) and KEGG pathways analysis revealed that most of the differential abundance proteins were found to be involved in energy and carbohydrate metabolism, photosynthesis, protein metabolism, stress and defense, metal detoxification, and cell wall reorganization. Our results suggest that the downregulation of chlorophyll biosynthetic proteins involved in photosynthesis were consistent with reduced chlorophyll content. The increased abundance of proteins involved in stress and defense indicates that these DAPs might provide significant insights into the adaptation of Brassica seedlings to Cu stress. The abundances of key proteins were further verified by monitoring the mRNA expression level of the respective transcripts. Taken together, these findings provide a potential molecular mechanism towards Cu stress tolerance and open a new route in accelerating the phytoextraction of Cu through exogenous application of CA in B. napus.

Characterization and fine mapping of a new dwarf mutant in Brassica napus

BACKGROUND

Plant height is an important plant characteristic closely related to yield performance of many crops. Reasonable reduction of plant height of crops is beneficial for improving yield and enhancing lodging resistance.

RESULTS

In the present study, we described the Brassica napus dwarf mutant bnd2 that was isolated using ethyl methanesulfonate (EMS) mutagenesis. Compared to wild type (WT), bnd2 exhibited reduced height and shorter hypocotyl and petiole leaves. By crossing the bnd2 mutant with the WT strain, we found that the ratio of the mutant to the WT in the F₂ population was close to 1:3, indicating that bnd2 is a recessive mutation of a single locus. Following bulked segregant analysis (BSA) by resequencing, BND2 was found to be located in the 13.77-18.08 Mb interval of chromosome A08, with a length of 4.31 Mb. After fine mapping with single nucleotide polymorphism (SNP) and insertion/deletion (InDel) markers, the gene was narrowed to a 140-Kb interval ranging from 15.62 Mb to 15.76 Mb. According to reference genome annotation, there were 27 genes in the interval, of which BnaA08g20960D had an SNP type variation in the intron between the mutant and its parent, which may be the candidate gene corresponding to BND2. The hybrid line derived from a cross between the mutant bnd2 and the commercial cultivar L329 had similar plant height but higher grain yield compared to the commercial cultivar, suggesting that the allele bnd2 is beneficial for hybrid breeding of lodging resistant and high yield rapeseed.

CONCLUSION

In this study, we identified a novel dwarf mutant of rapeseed with a new locus, which may be useful for functional analyses of genetic mechanisms of plant architecture and grain yield in rapeseed.

Phosphoproteomic Analysis of Thermomorphogenic Responses in Arabidopsis

Plants rapidly adapt to elevated ambient temperature by adjusting their growth and developmental programs. To date, a number of experiments have been carried out to understand how plants sense and respond to warm temperatures. However, how warm temperature signals are relayed from thermosensors to transcriptional regulators is largely unknown. To identify new early regulators of plant thermo-responsiveness, we performed phosphoproteomic analysis using TMT (Tandem Mass Tags) labeling and phosphopeptide enrichment with Arabidopsis etiolated seedlings treated with or without 3h of warm temperatures (29°C). In total, we identified 13,160 phosphopeptides in 5,125 proteins with 10,700 quantifiable phosphorylation sites. Among them, 200 sites (180 proteins) were upregulated, while 120 sites (87 proteins) were downregulated by elevated temperature. GO (Gene Ontology) analysis indicated that phosphorelay-related molecular function was enriched among the differentially phosphorylated proteins. We selected ATL6 (ARABIDOPSIS TOXICOS EN LEVADURA 6) from them and expressed its native and phosphorylation-site mutated (S343A S357A) forms in Arabidopsis and found that the mutated form of ATL6 was less stable than that of the native form both in vivo and in cell-free degradation assays. Taken together, our data revealed extensive protein phosphorylation during thermo-responsiveness, providing new candidate proteins/genes for studying plant thermomorphogenesis in the future.

Quantitative Proteomic Analysis of ER Stress Response Reveals both Common and Specific Features in Two Contrasting Ecotypes of Arabidopsis thaliana

Accumulation of unfolded and misfolded proteins in endoplasmic reticulum (ER) elicits a well-conserved response called the unfolded protein response (UPR), which triggers the upregulation of downstream genes involved in protein folding, vesicle trafficking, and ER-associated degradation (ERAD). Although dynamic transcriptomic responses and the underlying major transcriptional regulators in ER stress response in Arabidopsis have been well established, the proteome changes induced by ER stress have not been reported in Arabidopsis. In the current study, we found that the Arabidopsis Landsberg erecta (Ler) ecotype was more sensitive to ER stress than the Columbia (Col) ecotype. Quantitative mass spectrometry analysis with Tandem Mass Tag (TMT) isobaric labeling showed that, in total, 7439 and 7035 proteins were identified from Col and Ler seedlings, with 88 and 113 differentially regulated (FC > 1.3 or <0.7, p < 0.05) proteins by ER stress in Col and Ler, respectively. Among them, 40 proteins were commonly upregulated in Col and Ler, among which 10 were not upregulated in bzip28 bzip60 double mutant (Col background) plants. Of the 19 specifically upregulated proteins in Col, as compared with that in Ler, components in ERAD, N-glycosylation, vesicle trafficking, and molecular chaperones were represented. Quantitative RT-PCR showed that transcripts of eight out of 19 proteins were not upregulated (FC > 1.3 or <0.7, p < 0.05) by ER stress in Col ecotype, while transcripts of 11 out of 19 proteins were upregulated by ER stress in both ecotypes with no obvious differences in fold change between Col and Ler. Our results experimentally demonstrated the robust ER stress response at the proteome level in plants and revealed differentially regulated proteins that may contribute to the differed ER stress sensitivity between Col and Ler ecotypes in Arabidopsis.

Label-free comparative proteomic and physiological analysis provides insight into leaf color variation of the golden-yellow leaf mutant of Lagerstroemia indica

GL1 is a golden-yellow leaf mutant that cultivated from natural bud-mutation of Lagerstroemia indica and has a very low level of photosynthetic pigment under sunlight. GL1 can gradually increase its pigment content and turn into pale-green leaf when shading under sunshade net (referred as Re-GL1). The mechanisms that cause leaf color variation are complicated and are not still unclear. Here, we have used a label-free comparative proteomics to investigate differences in proteins abundance and analyze the specific biological process associated with mechanisms of leaf color variation in GL1. A total of 245 and 160 proteins with different abundance were identified in GL1 vs WT and GL1 vs Re-GL1, respectively. Functional classification analysis revealed that the proteins with different abundance mainly related to photosynthesis, heat shock proteins, ribosome proteins, and oxidation-reduction. The proteins that the most significantly contributed to leaf color variation were photosynthetic proteins of PSII and PSI, which directly related to photooxidation and determined the photosynthetic performance of photosystem. Further analysis demonstrated that low jasmonic acid content was needed to golden-yellow leaf GL1. These findings lay a solid foundation for future studies into the molecular mechanisms that underlie leaf color formation of GL1. BIOLOGICAL SIGNIFICANCE: The natural bud mutant GL1 of L. indica is an example through changing leaf color to cope with complex environment. However, the molecular mechanism of leaf color variation are largely elusive. The proteins with different abundance identified from a label-free comparative proteomics revealed a range of biological processes associated with leaf color variation, including photosynthesis, oxidation-reduction and jasmonic acid signaling. The photooxidation and low level of jasmonic acid played a primary role in GL1 adaptation in golden-yellow leaf. These findings provide possible pathway or signal for the molecular mechanism associated with leaf color formation and as a valuable resource for signal transaction of chloroplast.