Enhancing rice panicle branching and grain yield through tissue-specific brassinosteroid inhibition.

Crop yield potential is constrained by the inherent trade-offs among traits such as between grain size and number. Brassinosteroids (BRs) promote grain size, yet their role in regulating grain number is unclear. By deciphering the clustered-spikelet rice germplasm, we show that activation of the BR catabolic gene BRASSINOSTEROID-DEFICIENT DWARF3 (BRD3) markedly increases grain number. We establish a molecular pathway in which the BR signaling inhibitor GSK3/SHAGGY-LIKE KINASE2 phosphorylates and stabilizes OsMADS1 transcriptional factor, which targets TERMINAL FLOWER1-like gene RICE CENTRORADIALIS2. The tissue-specific activation of BRD3 in the secondary branch meristems enhances panicle branching, minimizing negative effects on grain size, and improves grain yield. Our study showcases the power of tissue-specific hormonal manipulation in dismantling the trade-offs among various traits and thus unleashing crop yield potential in rice.

Proteomics analysis of Cyclobalanopsis gilva provides new insights of low seed germination.

A valuable plant, Cyclobalanopsis gilva, (C. gilva) has a low germination rate (below 50%) under its natural habitations. In order to examine the reasons for the low germination rate, the seeds of C. gilva (germinated and non-germinated) were evaluated using comparative proteomics analysis. A total of 3078 differentially abundant proteins (DAPs) were identified through a label-free method; most DAPs up-accumulated in germinated seeds were related to carbohydrates metabolism. Furthermore the proteins related to the signals, stress, and protein metabolism showed up-accumulation in germinated and no abundance or down-accumulation in non-germinated seeds. Enzyme activity of HK, PGK, PFK, and PK from glycolysis in SG-Control samples were 1.7-, 1.1-, 1.4-, and 1.3-times higher compared with those in control ones while CS, NAD-MDH, α-KGDH, and ICDH from the TCA cycle in SG-Control samples were 3, 1.1, 1.2, and 1.2 times higher than those in NG-Control ones. The ß-amylase activity was 4-fold higher in successfully germinated seeds compared to non-germinated seeds. Interestingly, α-amylase did not show significant changes in protein abundance and enzyme activity among the three samples. The present findings reveal that unsuccessful germination of C. gilva seeds is due to lack of energy.

[Dynamic evaluation and driving forces of ecosystem services in Quanzhou bay estuary wetland, China]. / 泉州湾河口湿地生态系统服务价值的动态评价及驱动力分析.

Ecosystem service value (ESV) in 1997, 2005, 2013 and 2015 of Quanzhou Bay estuary wetland was evaluated dynamicly by market value, alternative value and opportunity cost methods, combined with classification of service indicators and deduplicate computing. The main driving forces for the changes of ESV and the pathway and intensity of their actions were identified using stepwise regression and path analysis methods. The results showed that the main ecosystem services of Quanzhou Bay estuary wetland were flood regulation, climate regulation, and food supply, which were directly driven by water supply, mariculture carrying capacity, and gross value of the regional production. Other drivers exerted indirect effect on the changes of main ESVs.

Proteomic and physiological responses in mangrove Kandelia candel roots under short-term high-salinity stress.

Kandelia candel is one of the mangrove species that are most resistant to environmental stress. As a typical nonsalt-secreting mangrove plant, K. candel is an ideal biological material to analyze the molecular mechanism of salt tolerance in woody plants. In this study, changes in protein abundance and expression profile in K. candel roots under high-salinity stress of 600 mmol L-1 NaCl were analyzed using isobaric tags for relative and absolute quantification (iTRAQ) assay. Moreover, the physiological parameters associated with metabolic pathways in which the differentially abundant proteins (DAPs) are involved were determined. A total of 5577 proteins were identified by iTRAQ analysis of the K. candel root proteins, of which 227 were DAPs with a fold change ratio >1.2 or a fold change ratio <0.83 and a P-value <0.05. A total of 227 DAPs consisting of 110 up-regulated and 117 down-regulated proteins were identified. Our Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed that the DAPs were primarily involved in biological processes including carbohydrate and energy metabolisms, stress response and defense, cell wall structure, and secondary metabolism. The results of the physiological parameters showed that their profile changes were consistent with those of the proteome analysis. The results of the proteome and physiological parameters showed that K. candel roots could resist high-salinity stress by maintaining a normal Embden-Meyerhof-Parnas and tricarboxylic acid (EMP-TCA) pathway, increasing the activities of various antioxidant enzymes and antioxidant contents, stabilizing the cell wall structure, and accumulating secondary metabolites such as triterpenoids.

Protein acetylation as a mechanism for Kandelia candel's adaption to daily flooding.

To explore the adaptation mechanisms of Kandelia candel (L.) Druce in response to daily flooding, a large-scale quantitative lysine acetylome was carried out using immunoaffinity enrichment of Lys-acetylated peptides and liquid chromatography linked to tandem mass spectrometry. A total of 1041 lysine acetylation (LysAc) sites, 1021 Lys-acetylated peptides and 617 Lys-acetylated proteins were identified. Six conserved sequence motifs of the LysAc sites, including a new motif KxxxxK, were detected. Among these proteins, 260 were differentially acetylated in response to flooding, which were preferentially predicted to participate in carbon metabolism and photosynthesis pathways based on KEGG pathway category enrichment analysis. Consistently, the transcriptional level of acetyltransferase and the consumption of acetyl-CoA were up-regulated under flooding conditions. Most of physiological parameters and mRNA expression levels related to carbon metabolism and photosynthesis were found to be insignificantly affected by flooding. Taken together, reversible protein LysAc is likely to be a post-translational mechanism contributing to the mangrove K. candel's adaptation to daily flooding.

Phosphoproteomics unveils stable energy supply as key to flooding tolerance in Kandelia candel.

The mangrove Kandelia candel (L.) Druce experiences daily flooding cycles. To explore the molecular mechanism underlying the physiological adaptation of K. candel to flooding, the potential role of protein phosphorylation in flooding responses was investigated by a large-scale quantitative phosphoproteomic analysis using isobaric tag for relative and absolute quantitation. Total 2141 unique phosphopeptides and 2603 non-redundant phosphorylation sites were identified from 1516 phosphoproteins in K. candel leaves. In addition to known phosphorylation motifs, three new motifs [GSP], [GxxSP] and [RSxS] were discovered. The phosphorylation levels of 96 differentially expressed phosphoproteins, including those involved in pyruvate metabolism and energy production, were identified in response to flooding. The physiological parameters and transcriptional levels relevant to flooding responses including photosynthesis, pyruvate metabolism, and ROS production were investigated and all were found to be robust under flooding conditions. The consistent results of the phosphoproteomic, physiological analyses and transcriptional levels reinforce each other to demonstrate that K. candel adapts to flooding through maintaining sufficient photosynthesis activities, achieving effective anaerobic respiration and increasing pentose phosphate pathway flux. Protein phosphorylation is likely to play a major role in the regulation of these pathways which together contribute to stable energy supply that enhances flooding tolerance in K. candel. BIOLOGICAL SIGNIFICANCE: Flooding stress is one of the major environmental stresses. The woody mangrove Kandelia candel experiences daily flooding cycles in its natural habitat. Protein phosphorylation is a crucial regulatory mechanism in plants' responses to both biotic and abiotic stresses. To analyze phosphorylation levels in critical enzymes involved in key metabolic pathways, we employed phosphoproteomic approach to dissect the adaptive mechanism of K. candel to flooding conditions. To our knowledge, this is the first large-scale quantitative phosphoproteomic analyses of K. candel's flooding responses. Multiplex iTRAQ-based quantitative proteomic and Nano-LC-MS/MS methods were used to construct the phosphorproteome. Our results indicate that K. candel is able to acquire stable energy supply under flooding by maintaining sufficient photosynthesis activities, enhancing effective anaerobic respiration and increasing pentose phosphate pathway (PPP) flux. The protein phosphorylation found in photosynthesis, anaerobic respiration and PPP is likely to play important roles in the flooding tolerance of K. candel.

Regulation of Anthocyanin Biosynthesis in Purple Leaves of Zijuan Tea (Camellia sinensis var. kitamura).

Plant anthocyanin biosynthesis is well understood, but the regulatory mechanism in purple foliage tea remains unclear. Using isobaric tag for relative and absolute quantification (iTRAQ), 815 differential proteins were identified in the leaves of Zijuan tea, among which 20 were associated with the regulation of anthocyanin metabolism. We found that the abundances of anthocyanin synthesis-related enzymes such as chalcone synthase, chalcone isomerase, dihydroflavonol 4-reductase and anthocyanin synthetase, as well as anthocyanin accumulation-related UDP-glucosyl transferase and ATP-binding cassette (ABC) transporters in the purple leaves were all significantly higher than those in the green leaves. The abundances of the transcription factors bHLH and HY5, regulating anthocyanin biosynthesis at transcriptional level were also obviously higher in purple leaves than those in green leaves. In addition, bifunctional 3-dehydroquinate dehydratase and chorismate mutase in purple leaves were distinctly higher in abundance compared to green leaves, which provided sufficient phenylalanine substrate for anthocyanin synthesis. Furthermore, lignin synthesis was found to be reduced due to the lower abundances of cinnamoyl-CoA reductase 1, peroxidase 15 and laccase-6, which resulted in increase of intermediates flow into anthocyanin synthesis pathway. The physiological data were consistent with proteomic results. These four aspects of biosynthetic regulation contribute to anthocyanin accumulation in purple leaves of Zijuan tea.

A multilevel investigation to discover why Kandelia candel thrives in high salinity.

The halophilic mangrove species Kandelia candel is an excellent model for understanding why halophytes thrive in high salinity. Preliminary transcriptomic analyses revealed that genes involved in diverse functions, such as in phenylpropanoid and amino acid metabolisms, and those in DNA replication and damage repair were highly responsive to salt stress. Proteomic analyses revealed that the proteins involved in light reaction of photosynthesis, amino acid and carbohydrate metabolisms, secondary metabolite biosynthesis and posttranslational modification showed increased levels in response to salt stress. The metabolisms of phenylpropanoids and amino acids under salt stress were systematically examined based on the preliminary omics analyses. The activities of phenylpropanoid biosynthetic enzymes and the contents of phenols, flavonoids, anthocyanins and lignins were significantly increased under salt stress. In the free amino acid pool, glutamate was the most abundant. Together with γ-aminobutyric acid, glutamate levels further increased, while proline levels remained unchanged in response to salt stress. These findings point to the potential importance of phenylpropanoids and free amino acids in salt tolerance of K. candel that have been observed, but not systemically investigated at the levels of gene expression, enzyme activity and metabolite accumulation in glycophytes and non-tree halophytes.

Proteomic approach reveals that starch degradation contributes to anthocyanin accumulation in tuberous root of purple sweet potato.

UNLABELLED: A comparative proteomic approach was carried out to investigate anthocyanin biosynthesis in the tuberous roots of yellow sweet potato (YSP) and purple sweet potato (PSP) cultivars. More than 800 proteins were reproducibly detected through two-dimensional electrophoresis (2-DE), of which 50 proteins with 39 more and 11 less accumulated in PSP were identified through matrix-assisted laser desorption ionization-time of flight/time of flight mass spectrometry (MALDI-TOF/TOF-MS). Most of the analyzed proteins are annotated to be involved in starch metabolism and glycolysis. The more abundant starch phosphorylase (SP) and phosphoglucomutase (PGM) in PSP promoted the synthesis of precursors for anthocyanin synthesis. The results implied that starch degradation provided abundant substrates for anthocyanin biosynthesis in tuberous roots of PSP. 24kDa vacuolar protein (VP24) is related to anthocyanin transport and accumulation in vacuoles. Vacuole-associated annexin protein, VCaB42, is correlated with tonoplast biogenesis. Synergistic action of the two proteins is probably involved in the microautophagy and the intravacuolar trapping of anthocyanins. Interestingly, both VCaB42 and VP24 were more accumulated in PSP, suggesting that anthocyanins generated in the cytosol were transported into and became stored in the vacuoles of PSP. The present study provides new insights into the mechanism of tuberous root-specific anthocyanin accumulation in PSP. BIOLOGICAL SIGNIFICANCE: Sweet potato ranks as the seventh most important crop worldwide. Purple sweet potato, a special sweet potato cultivar, has been extensively investigated because large amounts of anthocyanin accumulate in its tuberous roots. Anthocyanin is well known for its free radical-scavenging activity and beneficial effects on human health. Its biosynthetic pathway has been well characterized in model plants. Although large-scale systematic studies have been performed to identify the proteins present in sweet potato, information on the regulation of anthocyanin synthesis in sweet potato is insufficient. Our proteome study demonstrated that starch degradation may contribute to anthocyanin accumulation in purple sweet potato. To our knowledge, this study is the first to propose that starch degradation may provide precursors of anthocyanin biosynthesis in sweet potato.

Proteomic analysis of changes in the Kandelia candel chloroplast proteins reveals pathways associated with salt tolerance.

The plant chloroplast is one of the most sensitive organelles in response to salt stress. Chloroplast proteins extracted from seedling leaves were separated by two-dimensional gel electrophoresis (2-DE). More than 600 protein spots could be distinguished on each gel. Fifty-eight differentially expressed protein spots were detected, of which 46 could be identified through matrix-assisted laser desorption ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF-MS). These proteins were found to be involved in multiple aspects of chloroplast metabolism pathways such as photosynthesis, ATP synthesis, detoxification and antioxidation processes, nitrogen assimilation and fixation, protein metabolism, and tetrapyrrole biosynthesis. The results indicated that K. candel could withstand up to 500 mM NaCl stress for a measured period of 3 days, by maintaining normal or high photosynthetic electron transfer efficiency and an only slightly stimulated Calvin cycle. Meanwhile, we found that ROS scavenging, nitrogen assimilation, protein degradation and chaperone function in chloroplasts were also of importance for salt tolerance of K. candel. The ultrastructural and physiological data agree with chloroplast proteome results. These findings allow further exploration of our knowledge on salt adaptation in woody halophytes and may contribute to the development of more salt-tolerant plants in the future.