摘要：
<jats:title>Abstract</jats:title><jats:p>Lignocellulosic biomass is an abundant renewable feedstock, but its complex structure of lignocellulose poses barriers to its enzymatic hydrolysis and fermentation. Fungi possess diverse lignocellulolytic enzyme systems that synergistically deconstruct lignocellulose into soluble sugars for fermentation. This review elucidates recent advances in understanding the molecular mechanisms underpinning fungal degradation of lignocellulose. We analyze major enzyme classes tailored by fungi to depolymerize cellulose, hemicellulose, and lignin. Highlighted are the concerted actions and intimate partnerships between these biomass‐degrading enzymes. Current challenges impeding large‐scale implementation of enzymatic hydrolysis are discussed, along with emerging biotechnological opportunities. Advanced pretreatments, high‐throughput enzyme engineering platforms, and machine learning or artificial intelligence‐guided lignocellulolytic enzyme cocktail optimization represent promising ways to improve hydrolytic efficiencies. Elucidating the coordinated interplay and regulation of fungal lignocellulolytic machinery can facilitate optimization of fungal biotechnology platforms. Harnessing the efficiency of fungal biomass deconstruction promises to enhance the development of biorefinery processes for sustainable bioenergy.</jats:p>
摘要：
Ramie (Boehmeria nivea [L.] Gaud.), a nutritious animal feed, is rich in protein and produces a variety of secondary metabolites that increase its palatability and functional composition. Ethylene (ETH) is an important plant hormone that regulates the growth and development of various crops. In this study, we investigated the impact of ETH sprays on the growth and metabolism of forage ramie. We explored the mechanism of ETH regulation on the growth and secondary metabolites of forage ramie using transcriptomic and metabolomic analyses. Spraying ramie with ETH elevated the contents of flavonoids and chlorogenic acid and decreased the lignin content in the leaves and stems. A total of 1076 differentially expressed genes (DEGs) and 51 differentially expressed metabolites (DEMs) were identified in the leaves, and 344 DEGs and 55 DEMs were identified in the stems. The DEGs that affect phenylpropanoid metabolism, including BGLU41, LCT, PER63, PER42, PER12, PER10, POD, BAHD1, SHT, and At4g26220 were significantly upregulated in the leaves. Ethylene sprays downregulated tyrosine and chlorogenic acid (3-O-caffeoylquinic acid) in the leaves, but lignin biosynthesis HCT genes, including ACT, BAHD1, and SHT, were up- and downregulated. These changes in expression may ultimately reduce lignin biosynthesis. In addition, the upregulation of caffeoyl CoA-O-methyltransferase (CCoAOMT) may have increased the abundance of its flavonoids. Ethylene significantly downregulated metabolites, affecting phenylpropanoid metabolism in the stems. The differential 4CL and HCT metabolites were downregulated, namely, phenylalanine and tyrosine. Additionally, ETH upregulated 2-hydroxycinnamic acid and the cinnamyl hydroxyl derivatives (caffeic acid and p-coumaric acid). Cinnamic acid is a crucial intermediate in the shikimic acid pathway, which serves as a precursor for the biosynthesis of flavonoids and lignin. The ETH-decreased gene expression and metabolite alteration reduced the lignin levels in the stem. Moreover, the HCT downregulation may explain the inhibited lignin biosynthesis to promote flavonoid biosynthesis. In conclusion, external ETH application can effectively reduce lignin contents and increase the secondary metabolites of ramie without affecting its growth and development. These results provide candidate genes for improving ramie and offer theoretical and practical guidance for cultivating ramie for forage.
摘要：
Gibberellin regulates plant growth, development, and metabolic processes. However, the underlying mechanism of the substantial effect of gibberellin on stem height and secondary metabolites in forage ramie is unclear. Therefore, this study combined transcriptomic and metabolomics analyses to identify the mechanisms regulating growth and secondary metabolite contents in forage ramie following exogenous gibberellin application. Exogenous gibberellin application significantly reduced the lignin content in the leaves but not in the stems. At the same time, gibberellin significantly increased the total flavonoid and chlorogenic acid contents in both the stems and leaves. In addition, 293 differentially expressed genes (DEGs) and 68 differentially expressed metabolites (DEMs) were identified in the leaves. In the stems, 128 DEGs and 41 DEMs were identified. The DEGs PER42, FLS, CYP75A, and PNC1 were up-regulated in the leaves, affecting phenylpropane metabolism. The joint analysis of the DEMs and DEGs revealed that the changes in the DEGs and DEMs in the leaves and stems improved the substrate efficiency in the phenol propane pathway and inhibited lignin synthesis in plants, thus shifting to flavonoid pathway synthesis. In conclusion, gibberellin treatment effectively reduces the lignin content in forage ramie while increasing the flavonoid and chlorogenic acid contents. These findings provide empirical and practical guidance for breeding for forage quality in ramie and the improvement and cultivation control of forage ramie.
摘要：
Xyloglucan is an important component of hemicellulose, and xyloglucan oligosaccharides (Xh), which are metabolized by xyloglucan, play an important role in plant growth and development. However, the regulatory effects of the external application of Xh under cadmium (Cd) stress have not been determined. In this study, we evaluated the mechanism by which Xh contributes to resistance to Cd stress in ramie, a candidate plant species for toxic ion removal. The external application of Xh effectively attenuated the effects of Cd on ramie growth and photosynthetic pigments. Cd stress can also inhibit the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX), resulting in a significant increase in the extent of membrane lipid peroxidation. After the external application of Xh, antioxidant enzyme activity was up-regulated, and damage to membranes in plants was reduced. In addition, the external application of Xh increased Cd retention in roots, thereby significantly decreasing Cd content in shoots. The external application of Xh also regulated the subcellular distribution of Cd and increased the Cd content of the cell wall. In particular, a root cell wall analysis revealed that Cd+Xh treatment significantly increased the hemicellulose content in the cell wall and the amount of Cd retained. In summary, the external application of Xh alleviates Cd toxicity in ramie by increasing the hemicellulose content and the Cd fixation ability of the cell wall and by reducing membrane lipid peroxidation via antioxidant enzymes.
期刊：
International Journal of Molecular Sciences,2022年23(19):12025- ISSN：1661-6596
通讯作者：
De-Yu Xie<&wdkj&>Yucheng Jie
作者机构：
[Xie, De-Yu; Jie, Hongdong; Ma, Yushen; Jie, Yucheng] Hunan Agr Univ, Coll Agron, Changsha 410128, Peoples R China.;[Xie, De-Yu; Jie, Yucheng] Hunan Prov Engn Technol Res Ctr Grass Crop Germpl, Changsha 410128, Peoples R China.;[Xie, De-Yu] North Carolina State Univ, Dept Plant & Microbial Biol, Raleigh, NC 27695 USA.
通讯机构：
[De-Yu Xie; Yucheng Jie] A;Authors to whom correspondence should be addressed.<&wdkj&>Hunan Provincial Engineering Technology Research Center for Grass Crop Germplasm Innovation and Utilization, Changsha 410128, China<&wdkj&>Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA<&wdkj&>College of Agronomy, Hunan Agricultural University, Changsha 410128, China<&wdkj&>Authors to whom correspondence should be addressed.<&wdkj&>Hunan Provincial Engineering Technology Research Center for Grass Crop Germplasm Innovation and Utilization, Changsha 410128, China<&wdkj&>College of Agronomy, Hunan Agricultural University, Changsha 410128, China
摘要：
Ramie is one of the most significant fiber crops and contributes to good quality fiber. Drought stress (DS) is one of the most devastating abiotic factors which is accountable for a substantial loss in crop growth and production and disturbing sustainable crop production. DS impairs growth, plant water relation, and nutrient uptake. Ramie has evolved a series of defense responses to cope with DS. There are numerous genes regulating the drought tolerance (DT) mechanism in ramie. The morphological and physiological mechanism of DT is well-studied; however, modified methods would be more effective. The use of novel genome editing tools like clustered regularly interspaced short palindromic repeats (CRISPR) is being used to edit the recessive genes in crops to modify their function. The transgenic approaches are used to develop several drought-tolerant varieties in ramie, and further identification of tolerant genes is needed for an effective breeding plan. Quantitative trait loci (QTLs) mapping, transcription factors (TFs) and speed breeding are highly studied techniques, and these would lead to the development of drought-resilient ramie cultivars. The use of hormones in enhancing crop growth and development under water scarcity circumstances is critical; however, using different concentrations and testing genotypes in changing environments would be helpful to sort the tolerant genotypes. Since plants use various ways to counter DS, investigating mechanisms of DT in plants will lead to improved DT in ramie. This critical review summarized the recent advancements on DT in ramie using novel molecular techniques. This information would help ramie breeders to conduct research studies and develop drought tolerant ramie cultivars.
摘要：
<jats:p>Phytochelatins (PCs) play important roles in the detoxification of and tolerance to heavy metals in plants. The synthesis of PCs is catalyzed by phytochelatin synthase (PCS), which is activated by heavy metal ions. In this study, we isolated a <jats:italic>PCS</jats:italic> gene, <jats:italic>BnPCS1</jats:italic>, from the bast fiber crop ramie (<jats:italic>Boehmeria nivea</jats:italic>) using the RACE (rapid amplification of cDNA ends) method. The full-length <jats:italic>BnPCS1</jats:italic> cDNA is 1,949 bp in length with a 1,518 bp open reading frame (ORF) that encodes a 505 amino acid protein. The deduced BnPCS1 protein has a conserved N-terminus containing the catalytic triad Cys<jats:sup>58</jats:sup>, His<jats:sup>164</jats:sup>, Asp<jats:sup>182</jats:sup>, and a flexible C-terminal region containing a C<jats:sup>371</jats:sup>C<jats:sup>372</jats:sup>QETC<jats:sup>376</jats:sup>VKC<jats:sup>379</jats:sup> motif. The <jats:italic>BnPCS1</jats:italic> promoter region contains several cis-acting elements involved in phytohormone or abiotic stress responses. Subcellular localization analysis indicates that the BnPCS1-GFP protein localizes to the nucleus and the cytoplasm. Real-time PCR assays show that the expression of <jats:italic>BnPCS1</jats:italic> is significantly induced by cadmium (Cd) and the plant hormone abscisic acid (ABA). Overexpression lines of <jats:italic>BnPCS1</jats:italic> exhibited better root growth and fresh weight, lower level of MDA and H<jats:sub>2</jats:sub>O<jats:sub>2</jats:sub>, and higher Cd accumulation and translocation factor compared to the WT under Cd stress. Taken together, these results could provide new gene resources for phytoremediation of Cd-contaminated soils.</jats:p>
作者机构：
[Wang, Dong; Jie, YuCheng] Hunan Agr Univ, Ramie Res Inst, Changsha 410128, Hunan, Peoples R China.;[Zhu, ShouJing] Yichun Univ, Coll Life Sci Resources & Environm, Yichun 336000, Jiangxi, Peoples R China.;[Li, Xiang; Hu, ZhiXin; Zeng, Rui] Hunan Airbluer Environm Protect Technol, Changsha 410000, Hunan, Peoples R China.;[Lu, YanWei] Shenzhen Yupon Environm Protect Technol, Shenzhen 518000, CO, Peoples R China.
通讯机构：
[Jie, YuCheng] H;Hunan Agr Univ, Ramie Res Inst, Changsha 410128, Hunan, Peoples R China.
摘要：
<jats:title>Abstract</jats:title><jats:p>This study aimed to analyze the heavy metal absorption characteristics of different plant species and planting patterns on lead (Pb) and arsenic (As) levels in soil. Two ramie [<jats:italic>Boehmeria nivea</jats:italic> (L.) Guad.] varieties (Zhongzhu‐1 and Xiangzhu‐3), and <jats:italic>Pteris vittata</jats:italic> L. were cultivated in monoculture and intercropping patterns in soil polluted with heavy metals (Pb and As). The plant traits and biomasses of Zhongzhu‐1 and Xiangzhu‐3 intercropped with <jats:italic>P. vittata</jats:italic> at a high density were not significantly different compared to their individual monoculture treatments. Meanwhile, the biomass of <jats:italic>P. vittata</jats:italic> intercropped with ramie was significantly reduced. In addition, the Pb content and Pb accumulation in shoots of Zhongzhu‐1 and Xiangzhu‐3 intercropped with <jats:italic>P. vittata</jats:italic> at high density significantly increased compared with the Pb content and Pb accumulation from monoculture shoots. The Xiangzhu‐3/<jats:italic>P. vittata</jats:italic> high density intercropping system had the highest Pb extraction at 232.14ghm<jats:sup>−2</jats:sup> and a Pb extraction efficiency of 0.0222%. The <jats:italic>P. vittata</jats:italic> monoculture system had the highest As extraction with 225.87ghm<jats:sup>−2</jats:sup> and an As extraction efficiency of 0.2765%. Moreover, ramie and <jats:italic>P. vittata</jats:italic> intercropping at high density was the most efficacious planting method for minimizing Pb–As pollution in soil with higher and effective remediation efficiency and economic benefit than monoculture plantingsystem.</jats:p>
摘要：
MYB-related transcription factors play important roles in plant development and response to various environmental stresses. In the present study, a novel MYB gene, designated as BnMYB2 (GenBank accession number: MF741319.1), was isolated from Boehmeria nivea using rapid amplification of cDNA ends (RACE) and RT-PCR on a sequence fragment from a ramie transcriptome. BnMYB2 has a 945 bp open reading frame encoding a 314 amino acid protein that contains a DNA-binding domain and shares high sequence identity with MYB proteins from other plant species. The BnMYB2 promoter contains several putative cis-acting elements involved in stress or phytohormone responses. A translational fusion of BnMYB2 with enhanced green fluorescent protein (eGFP) showed nuclear and cytosolic subcellular localization. Real-time PCR results indicated that BnMYB2 expression was induced by Cadmium (Cd) stress. Overexpression of BnMYB2 in Arabidopsis thaliana resulted in a significant increase of Cd tolerance and accumulation. Thus, BnMYB2 positively regulated Cd tolerance and accumulation in Arabidopsis, and could be used to enhance the efficiency of Cd removal with plants.
摘要：
Zn and Fe are essential nutritional elements in plants and play important roles in various physiological processes of plants. Zn and Fe are chemically similar to cadmium (Cd); therefore, Zn and Fe may mediate Cd-induced physiological or metabolic changes in plants. In order to evaluate the interaction between Cd, Zn and Fe, we conducted a hydroponics experiment to determine the plant biomass, photosynthetic characteristics, and Cd accumulation of ten ramie cultivars under Zn/Fe-sufficient or Zn/Fe-deficient conditions in the presence of 32 mu M CdCl2. Ramie varied among cultivars in morpho-physiological response to Cd stress as well as Cd accumulation, translocation and distribution. Zn and Fe deficiency increased the concentration and amount of Cd in plant organs, but decreased TFstem to leaf and TFroot to stem. Cultivars with more Cd in roots and shoots showed smaller increase in Cd accumulation under Zn and Fe-deficiency stress. Xiangzhu 7 and Duobeiti 1 showed a higher capacity of Cd accumulation in their shoots. Zn and Fe deficiency decreased Pn, but increased Ci, Gs, and E in most cultivars. The difference in Cd translocation among ramie cultivars was mainly ascribed to the difference in plant transpiration.
