Genome-wide analysis of laccase genes in moso bamboo highlights PeLAC10 involved in lignin biosynthesis and in response to abiotic stresses

Genome-wide analysis of the common bean (Phaseolus vulgaris) laccase gene family and its functions in response to abiotic stress

BACKGROUND

Laccase (LAC) gene family plays a pivotal role in plant lignin biosynthesis and adaptation to various stresses. Limited research has been conducted on laccase genes in common beans.

RESULTS

29 LAC gene family members were identified within the common bean genome, distributed unevenly in 9 chromosomes. These members were divided into 6 distinct subclades by phylogenetic analysis. Further phylogenetic analyses and synteny analyses indicated that considerable gene duplication and loss presented throughout the evolution of the laccase gene family. Purified selection was shown to be the major evolutionary force through Ka / Ks. Transcriptional changes of PvLAC genes under low temperature and salt stress were observed, emphasizing the regulatory function of these genes in such conditions. Regulation by abscisic acid and gibberellins appears to be the case for PvLAC3, PvLAC4, PvLAC7, PvLAC13, PvLAC14, PvLAC18, PvLAC23, and PvLAC26, as indicated by hormone induction experiments. Additionally, the regulation of PvLAC3, PvLAC4, PvLAC7, and PvLAC14 in response to nicosulfuron and low-temperature stress were identified by virus-induced gene silence, which demonstrated inhibition on growth and development in common beans.

CONCLUSIONS

The research provides valuable genetic resources for improving the resistance of common beans to abiotic stresses and enhance the understanding of the functional roles of the LAC gene family.

Identification of a novel marker and its associated laccase gene for regulating ear length in tropical and subtropical maize lines

KEY MESSAGE

This study revealed the identification of a novel gene, Zm00001d042906, that regulates maize ear length by modulating lignin synthesis and reported a molecular marker for selecting maize lines with elongated ears. Maize ear length has garnered considerable attention due to its high correlation with yield. In this study, six maize inbred lines of significant importance in maize breeding were used as parents. The temperate maize inbred line Ye107, characterized by a short ear, was crossed with five tropical or subtropical inbred lines featuring longer ears, creating a multi-parent population displaying significant variations in ear length. Through genome-wide association studies and mutation analysis, the A/G variation at SNP_183573532 on chromosome 3 was identified as an effective site for discriminating long-ear maize. Furthermore, the associated gene Zm00001d042906 was found to correlate with maize ear length. Zm00001d042906 was functionally annotated as a laccase (Lac4), which showed activity and influenced lignin synthesis in the midsection cells of the cob, thereby regulating maize ear length. This study further reports a novel molecular marker and a new gene that can assist maize breeding programs in selecting varieties with elongated ears.

The Laccase Family Gene CsLAC37 Participates in Resistance to Colletotrichum gloeosporioides Infection in Tea Plants

Fungal attacks have become a major obstacle in tea plantations. Colletotrichum gloeosporioides is one of the most devastating fungal pathogens in tea plantations that can severely affect tea yield and quality. However, the molecular mechanism of resistance genes involved in anthracnose is still largely unknown in tea plants. Here, we found that the laccase gene CsLAC37 was involved in the response to fungal infection based on a transcriptome analysis. The full-length CDS of CsLAC37 was cloned, and its protein sequence had the closest relationship with the Arabidopsis AtLAC15 protein compared to other AtLACs. Tissue-specific expression analysis showed that CsLAC37 had higher expression levels in mature leaves and stems than in the other tissues. Subcellular localization showed that the CsLAC37 protein was predominantly localized in the cell membrane. The expression levels of CsLAC37 were upregulated at different time points under cold, salt, SA, and ABA treatments. qRT-PCR confirmed that CsLAC37 responded to both Pestalotiopsis-like species and C. gloeosporioides infections. Functional validation showed that the hydrogen peroxide (H2O2) content increased significantly, and POD activity decreased in leaves after antisense oligonucleotide (AsODN) treatment compared to the controls. The results demonstrated that CsLAC37 may play an important role in resistance to anthracnose, and the findings provide a theoretical foundation for molecular breeding of tea varieties with resistance to fungal diseases.

Caffeine Produced in Rice Plants Provides Tolerance to Water-Deficit Stress

Exogenous or endogenous caffeine application confers resistance to diverse biotic stresses in plants. In this study, we demonstrate that endogenous caffeine in caffeine-producing rice (CPR) increases tolerance even to abiotic stresses such as water deficit. Caffeine produced by CPR plants influences the cytosolic Ca2+ ion concentration gradient. We focused on examining the expression of Ca2+-dependent protein kinase genes, a subset of the numerous proteins engaged in abiotic stress signaling. Under normal conditions, CPR plants exhibited increased expressions of seven OsCPKs (OsCPK10, OsCPK12, OsCPK21, OsCPK25, OsCPK26, OsCPK30, and OsCPK31) and biochemical modifications, including antioxidant enzyme (superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase) activity and non-enzymatic antioxidant (ascorbic acid) content. CPR plants exhibited more pronounced gene expression changes and biochemical alterations in response to water-deficit stress. CPR plants revealed increased expressions of 16 OsCPKs (OsCPK1, OsCPK2, OsCPK3, OsCPK4, OsCPK5, OsCPK6, OsCPK9, OsCPK10, OsCPK11, OsCPK12, OsCPK14, OsCPK16, OsCPK18, OsCPK22, OsCPK24, and OsCPK25) and 8 genes (OsbZIP72, OsLEA25, OsNHX1, OsRab16d, OsDREB2B, OsNAC45, OsP5CS, and OsRSUS1) encoding factors related to abiotic stress tolerance. The activity of antioxidant enzymes increased, and non-enzymatic antioxidants accumulated. In addition, a decrease in reactive oxygen species, an accumulation of malondialdehyde, and physiological alterations such as the inhibition of chlorophyll degradation and the protection of photosynthetic machinery were observed. Our results suggest that caffeine is a natural chemical that increases the potential ability of rice to cope with water-deficit stress and provides robust resistance by activating a rapid and comprehensive resistance mechanism in the case of water-deficit stress. The discovery, furthermore, presents a new approach for enhancing crop tolerance to abiotic stress, including water deficit, via the utilization of a specific natural agent.

Anatomical and Transcriptome Analyses of Moso Bamboo Culm Neck Growth: Unveiling Key Insights

The Moso bamboo culm neck, connected with the rhizome and the shoot bud, is an important hub for connecting and transporting the aboveground and belowground systems of bamboo for the shoot bud development and rapid growth. Our previous study revealed that the culm neck generally undergoes six different developmental stages (CNS1-CNS6), according to the primary thickening growth of the underground shoot bud. However, the molecular mechanism of the culm neck development remains unknown. The present study focused on the developmental process of the CNS3-CNS5 stages, representing the early, middle, and late elongation stages, respectively. These stages are densely packed with vascular tissues and consist of epidermis, hypodermis, cortex, and ground tissue. Unlike the hollow structure of the culms, the culm necks are solid structures. As the culm neck continues to grow, the lignin deposition increases noticeably, contributing to its progressive strengthening. For the transcriptome analysis, a total of 161,160 transcripts with an average length of 2373 were obtained from these stages using both PacBio and Illumina sequencing. A total of 92.2% of the reads mapped to the Moso bamboo reference genome. Further analysis identified a total of 5524 novel genes and revealed a dynamic transcriptome. Secondary-metabolism- and transport-related genes were upregulated particularly with the growth of the culm neck. Further analysis revealed the molecular processes of lignin accumulation in the culm neck, which include differentially expressed genes (DEGs) related to cell wall loosening and remodeling and secondary metabolism. Moreover, the upregulations of transcription factors such as MYBH and RSM in the MYB family play crucial roles during critical transitions in the culm neck development, such as changes in the angle between the rhizome and the culm neck. Our new findings provide essential insights into the cellular roadmaps, transcriptional networks, and key genes involved in the culm neck development.

Unveiling the biosynthesis, mechanisms, and impacts of miRNAs in drought stress resilience in plants

Drought stress is one of the most serious threats to sustainable agriculture and is predicted to be further intensified in the coming decades. Therefore, understanding the mechanism of drought stress tolerance and the development of drought-resilient crops are the major goals at present. In recent years, noncoding microRNAs (miRNAs) have emerged as key regulators of gene expressions under drought stress conditions and are turning out to be the potential candidates that can be targeted to develop drought-resilient crops in the future. miRNAs are known to target and decrease the expression of various genes to govern the drought stress response in plants. In addition, emerging evidence also suggests a regulatory role of long non-coding RNAs (lncRNAs) in the regulation of miRNAs and the expression of their target genes by a process referred as miRNA sponging. In this review, we present the regulatory roles of miRNAs in the modulation of drought-responsive genes along with discussing their biosynthesis and action mechanisms. Additionally, the interactive roles of miRNAs with phytohormone signaling components have also been highlighted to present the global view of miRNA functioning under drought-stress conditions.

Influence of Planting Density on Sweet Potato Storage Root Formation by Regulating Carbohydrate and Lignin Metabolism

An appropriate planting density could realize the maximum yield potential of crops, but the mechanism of sweet potato storage root formation in response to planting density is still rarely investigated. Four planting densities, namely D15, D20, D25, and D30, were set for 2-year and two-site field experiments to investigate the carbohydrate and lignin metabolism in potential storage roots and its relationship with the storage root number, yield, and commercial characteristics at the harvest period. The results showed that an appropriate planting density (D20 treatment) stimulated cambium cell differentiation, which increased carbohydrate accumulation and inhibited lignin biosynthesis in potential storage roots. At canopy closure, the D20 treatment produced more storage roots, particularly developing ones. It increased the yield by 10.18-19.73% compared with the control D25 treatment and improved the commercial features by decreasing the storage root length/diameter ratio and increasing the storage root weight uniformity. This study provides a theoretical basis for the high-value production of sweet potato.

Comprehensive analysis of the laccase gene family in tea plant highlights its roles in development and stress responses

BACKGROUND

Laccase (LAC) is the pivotal enzyme responsible for the polymerization of monolignols and stress responses in plants. However, the roles of LAC genes in plant development and tolerance to diverse stresses are still largely unknown, especially in tea plant (Camellia sinensis), one of the most economically important crops worldwide.

RESULTS

In total, 51 CsLAC genes were identified, they were unevenly distributed on different chromosomes and classified into six groups based on phylogenetic analysis. The CsLAC gene family had diverse intron-exon patterns and a highly conserved motif distribution. Cis-acting elements in the promoter demonstrated that promoter regions of CsLACs encode various elements associated with light, phytohormones, development and stresses. Collinearity analysis identified some orthologous gene pairs in C. sinensis and many paralogous gene pairs among C. sinensis, Arabidopsis and Populus. Tissue-specific expression profiles revealed that the majority of CsLACs had high expression in roots and stems and some members had specific expression patterns in other tissues, and the expression patterns of six genes by qRT‒PCR were highly consistent with the transcriptome data. Most CsLACs showed significant variation in their expression level under abiotic (cold and drought) and biotic (insect and fungus) stresses via transcriptome data. Among them, CsLAC3 was localized in the plasma membrane and its expression level increased significantly at 13 d under gray blight treatment. We found that 12 CsLACs were predicted to be targets of cs-miR397a, and most CsLACs showed opposite expression patterns compared to cs-miR397a under gray blight infection. Additionally, 18 highly polymorphic SSR markers were developed, these markers can be widely used for diverse genetic studies of tea plants.

CONCLUSIONS

This study provides a comprehensive understanding of the classification, evolution, structure, tissue-specific profiles, and (a)biotic stress responses of CsLAC genes. It also provides valuable genetic resources for functional characterization towards enhancing tea plant tolerance to multiple (a)biotic stresses.

Identification and Phylogenetic Analysis of the R2R3-MYB Subfamily in Brassica napus

The R2R3-MYB sub-family proteins are composed of most members of MYB (v-Myb avian myeloblastosis viral oncogene homolog) protein, a plant-specific transcription factor (TF) that is classified into four classes depending on the number of MYB repeats. R2R3-MYB TFs are involved in physiological and biochemical processes. However, the functions of the Brassica napus R2R3-MYB genes are still mainly unknown. In this study, 35 Brassica napus MYB (BnaMYB) genes were screened in the genome of Brassica napus, and details about their physical and chemical characteristics, evolutionary relationships, chromosome locations, gene structures, three-dimensional protein structures, cis-acting promoter elements, and gene duplications were uncovered. The BnaMYB genes have undergone segmental duplications and positive selection pressure, according to evolutionary studies. The same subfamilies have similar intron-exon patterns and motifs, according to the genes' structure and conserved motifs. Additionally, through cis-element analysis, many drought-responsive and other stress-responsive cis-elements have been found in the promoter regions of the BnaMYB genes. The expression of the BnaMYB gene displays a variety of tissue-specific patterns. Ten lignin-related genes were chosen for drought treatment. Our research screened four genes that showed significant upregulation under drought stress, and thus may be important drought-responsive genes. The findings lay a new foundation for understanding the complex mechanisms of BnaMYB in multiple developmental stages and pathways related to drought stress in rapeseed.

Genome-wide analysis of the laccase gene family in wheat and relationship with arbuscular mycorrhizal colonization

We identified 156 laccase genes belonging to 11 subfamilies in the wheat genome, and the natural variation of laccase genes significantly affected the development of wheat-arbuscular mycorrhizal symbiosis. Laccases (LACs) have a variety of functions in plant lignification, cell elongation and stress responses. This study aimed to reveal the phylogeny, chromosomal spatial distribution, coexpression and evolution of LAC genes in the wheat genome and to investigate the possible roles of LAC genes during arbuscular mycorrhizal (AM) symbiosis. The genomic characteristics of LAC genes were analyzed by using bioinformatics analysis methods, and the polymorphisms of LAC genes were analyzed by using a diverse wheat panel composed of 289 wheat cultivars. We identified 156 LAC genes belonging to 11 subfamilies in the wheat genome, and segmental duplication dominated the amplification of the LAC gene family in the wheat genome. LACs are dominantly located in the R2 region of wheat chromosomes. Some LACs are collinear with the characterized LACs in Arabidopsis thaliana or rice. A number of genes encoding transcription factors, kinases, and phosphatases were coexpressed with LAC genes in wheat. TaLACs may be potential targets for some miRNAs. Most TaLACs are mainly expressed in the roots and stems of plants. The expression of TaLACs could be regulated by the inoculation of Fusarium graminearum or AM fungi. The polymorphisms of TaLACs mainly accumulate by random drift instead of by selection. Through candidate gene association analysis, we found that the natural variations in TaLACs significantly affected root colonization by AM fungi. The present study provides useful information for further study of the biological functions of LAC genes in wheat, especially the roles of LAC genes during the development of AM symbiosis.

Feedstock design for quality biomaterials

Feedstock design is crucial for lignocellulosic biomass use. Current strategies for feedstock design cannot be readily applied to improve the quality of biomass-based materials, limiting the sustainability and economics of lignocellulosic biorefineries. Recent studies have advanced the understanding of biomass structure-property relationships and discovered several characteristics, such as molecular weight, uniformity, linkage profile, and functional groups, that are critical for manufacturing diverse quality biomaterials. These discoveries call for fundamentally different strategies for feedstock development. Such strategies need to rediscover the roles of monolignol biosynthesis enzymes and leverage lignin polymerization enzymes to achieve precise control of lignin molecular structure. These innovations could transform biomass into feedstock for high-quality biomaterials, addressing essential environmental challenges and empowering the bioeconomy.

Integrated multi-omics analysis uncovers roles of mdm-miR164b-MdORE1 in strigolactone-mediated inhibition of adventitious root formation in apple

Apple is one of the most important fruit crops in temperate regions and largely relies on cutting propagation. Adventitious root formation is crucial for the success of cutting propagation. Strigolactones have been reported to function in rooting of woody plants. In this study, we determined that strigolactones have inhibitory effects on adventitious root formation in apple. Transcriptome analysis identified 12 051 differentially expressed genes over the course of adventitious root initiation, with functions related to organogenesis, cell wall biogenesis or plant development. Further analysis indicated that strigolactones might inhibit adventitious root formation through repressing two core hub genes, MdLAC3 and MdORE1. Combining small RNA and degradome sequencing, as well as dual-luciferase sensor assays, we identified and validated three negatively correlated miRNA-mRNA pairs, including mdm-miR397-MdLAC3 and mdm-miR164a/b-MdORE1. Overexpression of mdm-miR164b and silencing MdORE1 exhibited enhanced adventitious root formation in tobacco and apple, respectively. Finally, we verified the role of mdm-miR164b-MdORE1 in strigolactone-mediated repression of rooting ability. Overall, the identified comprehensive regulatory network in apple not only provides insight into strigolactone-mediated adventitious root formation in other woody plants, but also points to a potential strategy for genetic improvement of rooting capacity in woody plants.

Identification of Competing Endogenous RNAs (ceRNAs) Network Associated with Drought Tolerance in Medicago truncatula with Rhizobium Symbiosis

Drought, bringing the risks of agricultural production losses, is becoming a globally environmental stress. Previous results suggested that legumes with nodules exhibited superior drought tolerance compared with the non-nodule group. To investigate the molecular mechanism of rhizobium symbiosis impacting drought tolerance, transcriptome and sRNAome sequencing were performed to identify the potential mRNA-miRNA-ncRNA dynamic network. Our results revealed that seedlings with active nodules exhibited enhanced drought tolerance by reserving energy, synthesizing N-glycans, and medicating systemic acquired resistance due to the early effects of symbiotic nitrogen fixation (SNF) triggered in contrast to the drought susceptible with inactive nodules. The improved drought tolerance might be involved in the decreased expression levels of miRNA such as mtr_miR169l-5p, mtr_miR398b, and mtr_miR398c and its target genes in seedlings with active nodules. Based on the negative expression pattern between miRNA and its target genes, we constructed an mRNA-miR169l-ncRNA ceRNA network. During severe drought stress, the lncRNA alternative splicings TCONS_00049507 and TCONS_00049510 competitively interacted with mtr_miR169l-5p, which upregulated the expression of NUCLEAR FACTOR-Y (NF-Y) transcription factor subfamily NF-YA genes MtNF-YA2 and MtNF-YA3 to regulate their downstream drought-response genes. Our results emphasized the importance of SNF plants affecting drought tolerance. In conclusion, our work provides insight into ceRNA involvement in rhizobium symbiosis contributing to drought tolerance and provides molecular evidence for future study.

Identification of KFB Family in Moso Bamboo Reveals the Potential Function of PeKFB9 Involved in Stress Response and Lignin Polymerization

The Kelch repeat F-box (KFB) protein is an important E3 ubiquitin ligase that has been demonstrated to perform an important post-translational regulatory role in plants by mediating multiple biological processes. Despite their importance, KFBs have not yet been identified and characterized in bamboo. In this study, 19 PeKFBs were identified with F-box and Kelch domains; genes encoding these PeKFBs were unevenly distributed across 12 chromosomes of moso bamboo. Phylogenetic analysis indicated that the PeKFBs were divided into eight subclades based on similar gene structures and highly conserved motifs. A tissue-specific gene expression analysis showed that the PeKFBs were differentially expressed in various tissues of moso bamboo. All the promoters of the PeKFBs contained stress-related cis-elements, which was supported by the differentially expression of PeKFBs of moso bamboo under drought and cold stresses. Sixteen proteins were screened from the moso bamboo shoots' cDNA library using PeKFB9 as a bait through a yeast two-hybrid (Y2H) assay. Moreover, PeKFB9 physically interacted with PeSKP1-like-1 and PePRX72-1, which mediated the activity of peroxidase in proteolytic turnover. Taken together, these findings improved our understanding of PeKFBs, especially in response to stresses, and laid a foundation for revealing the molecular mechanism of PeKFB9 in regulating lignin polymerization by degrading peroxidase.

Characterization of the ABC Transporter G Subfamily in Pomegranate and Function Analysis of PgrABCG14

ATP-binding cassette subfamily G (ABCG) proteins play important roles in plant growth and development by transporting metabolites across cell membranes. To date, the genetic characteristics and potential functions of pomegranate ABCG proteins (PgrABCGs) have remained largely unknown. In this study, we found that 47 PgrABCGs were divided into five groups according to a phylogenetic analysis; groups I, II, III, and IV members are half-size proteins, and group V members are full-size proteins. PgrABCG14, PgrABCG21, and PgrABCG47 were highly expressed in the inner seed coat but had very low expression levels in the outer seed coat, and the expression levels of these three PgrABCG genes in the inner seed coats of hard-seeded pomegranate ‘Dabenzi’ were higher than those of soft-seeded pomegranate ‘Tunisia’. In addition, the expression of these three PgrABCG genes was highly correlated with the expression of genes involved in lignin biosynthesis and hormone signaling pathways. The evolution of PgrABCG14 presents a highly similar trend to the origin and evolution of lignin biosynthesis during land plant evolution. Ectopic expression of PgrABCG14 in Arabidopsis promoted plant growth and lignin accumulation compared to wild type plants; meanwhile, the expression levels of lignin biosynthesis-related genes (CAD5, C4H, and Prx71) and cytokinin response marker genes (ARR5 and ARR15) were significantly upregulated in transgenic plants, which suggests the potential role of PgrABCG14 in promoting plant growth and lignin accumulation. Taken together, these findings not only provide insight into the characteristics and evolution of PgrABCGs, but also shed a light on the potential functions of PgrABCGs in seed hardness development.

Genome-wide analysis of the CAD gene family reveals two bona fide CAD genes in oil palm

Cinnamyl alcohol dehydrogenase (CAD) is the key enzyme for lignin biosynthesis in plants. In this study, genome-wide analysis was performed to identify CAD genes in oil palm (Elaeis guineensis). Phylogenetic analysis was then conducted to select the bona fide EgCADs. The bona fide EgCAD genes and their respective 5' flanking regions were cloned and analysed. Their expression profiles were evaluated in various organs using RT-PCR. Seven EgCAD genes (EgCAD1-7) were identified and divided into four phylogenetic groups. EgCAD1 and EgCAD2 display high sequence similarities with other bona fide CADs and possess all the signature motifs of the bona fide CAD. They also display similar 3D protein structures. Gene expression analysis showed that EgCAD1 was expressed most abundantly in the root tissues, while EgCAD2 was expressed constitutively in all the tissues studied. EgCAD1 possesses only one transcription start site, while EgCAD2 has five. Interestingly, a TC microsatellite was found in the 5' flanking region of EgCAD2. The 5' flanking regions of EgCAD1 and EgCAD2 contain lignin-associated regulatory elements i.e. AC-elements, and other defence-related motifs, including W-box, GT-1 motif and CGTCA-motif. Altogether, these results imply that EgCAD1 and EgCAD2 are bona fide CAD involved in lignin biosynthesis during the normal development of oil palm and in response to stresses. Our findings shed some light on the roles of the bona fide CAD genes in oil palm and pave the way for manipulating lignin content in oil palm through a genetic approach.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03208-0.

Overexpression of PeNAC122 gene promotes wood formation and tolerance to osmotic stress in poplars

Finding the adequate balance between wood formation and abiotic stress resistance is still an important challenge for industrial woody crops. In this study, PeNAC122, a member of the NAC transcription factor (TF) family highly expressed in xylem, was cloned from Populus euphratica. Tissue expression and β-glucuronidase (GUS) staining showed that PeNAC122 was exclusively expressed in phloem fiber and secondary xylem of stems. Subcellular and yeast transactivation assays confirmed that PeNAC122 protein existed in the nucleus and did not have transcriptional activation and inhibitory activity. Overexpression of PeNAC122 poplar lines exhibited reduced plant height, thickened xylem, and accumulated lignin content in stems, and also upregulates the expression of secondary cell wall biosynthetic genes. Moreover, overexpression of PeNAC122 lines displayed more tolerance to PEG6000-induced osmotic stress, with stronger photosynthetic performance, higher antioxidant enzyme activity, and less accumulation of reactive oxygen species in leaves, and higher expression levels of stress response genes DREB2A, RD29, and NCED3. These results indicate that PeNAC122 plays a crucial role in wood formation and abiotic stress tolerance, which, in addition to potential use in improving wood quality, provides further insight into the role of NAC family TFs in balancing wood development and abiotic stress resistance.

Genome-Wide Identification of Switchgrass Laccases Involved in Lignin Biosynthesis and Heavy-Metal Responses

Plant laccase genes belong to a multigene family, play key roles in lignin polymerization, and participate in the resistance of plants to biotic and abiotic stresses. Switchgrass is an important resource for forage and bioenergy production, yet information about the switchgrass laccase gene family is scarce. Using bioinformatic approaches, a genome-wide analysis of the laccase multigene family in switchgrass was carried out in this study. In total, 49 laccase genes (PvLac1 to PvLac49) were identified; these can be divided into five subclades, and 20 of them were identified as targets of miR397. The tandem and segmental duplication of laccase genes on Chr05 and Chr08 contributed to the expansion of the laccase family. The laccase proteins shared conserved signature sequences but displayed relatively low sequence similarity, indicating the potential functional diversity of switchgrass laccases. Switchgrass laccases exhibited distinct tissue/organ expression patterns, revealing that some laccases might be involved in the lignification process during stem development. All five of the laccase isoforms selected from different subclades responded to heavy metal. The immediate response of lignin-related laccases, as well as the delayed response of low-abundance laccases, to heavy-metal treatment shed light on the multiple roles of laccase isoforms in response to heavy-metal stress.

Involvement of Laccase2 in Cuticle Sclerotization of the Whitefly, Bemisia tabaci Middle East–Asia Minor 1

Cuticle sclerotization is critical for insect survival. Laccase2 (Lac2) is a phenol oxidase that plays a key role in cuticle formation and pigmentation in a variety of insects. However, the function of Lac2 in whitefly, Bemisia tabaci, remains unclear. In this study, we identified a BtLac2 gene in B. tabaci MEAM1 and found that BtLac2 was expressed in all stages. It was highly expressed in the egg stage, followed by nymph and adult. Moreover, the expression of BtLac2 was higher in the cuticle than in other tissues. Knockdown of BtLac2 in nymphs produced thinner and fragile cuticles, which significantly increased the mortality rate, extended the development duration of nymphs, and decreased the emergence rate of adults. This result demonstrates that BtLac2 plays an important role in the cuticle hardening of B. tabaci and suggests a potential management strategy using RNAi to knock down BtLac2 expression.

Transcriptional activation of rice CINNAMOYL-CoA REDUCTASE 10 by OsNAC5, contributes to drought tolerance by modulating lignin accumulation in roots

Drought is a common abiotic stress for terrestrial plants and often affects crop development and yield. Recent studies have suggested that lignin plays a crucial role in plant drought tolerance; however, the underlying molecular mechanisms are still largely unknown. Here, we report that the rice (Oryza sativa) gene CINNAMOYL-CoA REDUCTASE 10 (OsCCR10) is directly activated by the OsNAC5 transcription factor, which mediates drought tolerance through regulating lignin accumulation. CCR is the first committed enzyme in the monolignol synthesis pathway, and the expression of 26 CCR genes was observed to be induced in rice roots under drought. Subcellular localisation assays revealed that OsCCR10 is a catalytically active enzyme that is localised in the cytoplasm. The OsCCR10 transcript levels were found to increase in response to abiotic stresses, such as drought, high salinity, and abscisic acid (ABA), and transcripts were detected in roots at all developmental stages. In vitro enzyme activity and in vivo lignin composition assay suggested that OsCCR10 is involved in H- and G-lignin biosynthesis. Transgenic rice plants overexpressing OsCCR10 showed improved drought tolerance at the vegetative stages of growth, as well as higher photosynthetic efficiency, lower water loss rates, and higher lignin content in roots compared to non-transgenic (NT) controls. In contrast, CRISPR/Cas9-mediated OsCCR10 knock-out mutants exhibited reduced lignin accumulation in roots and less drought tolerance. Notably, transgenic rice plants with root-preferential overexpression of OsCCR10 exhibited higher grain yield than NT controls plants under field drought conditions, indicating that lignin biosynthesis mediated by OsCCR10 contributes to drought tolerance.

Identification and expression analysis of the glycosyltransferase GT43 family members in bamboo reveal their potential function in xylan biosynthesis during rapid growth

Background

Xylan is one of the most abundant hemicelluloses and can crosslink cellulose and lignin to increase the stability of cell walls. A number of genes encoding glycosyltransferases play vital roles in xylan biosynthesis in plants, such as those of the GT43 family. However, little is known about glycosyltransferases in bamboo, especially woody bamboo which is a good substitute for timber.

Results

A total of 17 GT43 genes (PeGT43–1 ~ PeGT43–17) were identified in the genome of moso bamboo (Phyllostachys edulis), which belong to three subfamilies with specific motifs. The phylogenetic and collinearity analyses showed that PeGT43s may have undergone gene duplication, as a result of collinearity found in 12 pairs of PeGT43s, and between 17 PeGT43s and 10 OsGT43s. A set of cis-acting elements such as hormones, abiotic stress response and MYB binding elements were found in the promoter of PeGT43s. PeGT43s were expressed differently in 26 tissues, among which the highest expression level was found in the shoots, especially in the rapid elongation zone and nodes. The genes coexpressed with PeGT43s were annotated as associated with polysaccharide metabolism and cell wall biosynthesis. qRT–PCR results showed that the coexpressed genes had similar expression patterns with a significant increase in 4.0 m shoots and a peak in 6.0 m shoots during fast growth. In addition, the xylan content and structural polysaccharide staining intensity in bamboo shoots showed a strong positive correlation with the expression of PeGT43s. Yeast one-hybrid assays demonstrated that PeMYB35 could recognize the 5′ UTR/promoter of PeGT43–5 by binding to the SMRE cis-elements.

Conclusions

PeGT43s were found to be adapted to the requirement of xylan biosynthesis during rapid cell elongation and cell wall accumulation, as evidenced by the expression profile of PeGT43s and the rate of xylan accumulation in bamboo shoots. Yeast one-hybrid analysis suggested that PeMYB35 might be involved in xylan biosynthesis by regulating the expression of PeGT43–5 by binding to its 5′ UTR/promoter. Our study provides a comprehensive understanding of PeGT43s in moso bamboo and lays a foundation for further functional analysis of PeGT43s for xylan biosynthesis during rapid growth.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08192-y.

Plant miR397 and its functions

MicroRNAs (miRNAs) are noncoding, small RNAs of 20-24 nucleotides (nt) and function critically at the post-transcriptional level to regulate gene expression through cleaving mRNA targets or interfering with translation of the target mRNAs. They are broadly involved in many biological processes in plants. The miR397 family in plants contains several conserved members either in 21-nt or in 22-nt that mainly target the laccase (LAC) genes functioning in lignin synthesis and are involved in the development of plants under various conditions. Recent findings showed that miR397b in Arabidopsis could also target to Casein Kinase II Subunit Beta 3 (CKB3) and mediate circadian regulation and plant flowering. This review aims to summarise recent updates on miR397 and provides the available basis for understanding the functional mechanisms of miR397 in plant growth and development regulation and in response to external adverse stimulation.

Genome-wide identification, evolution and expression analysis of the aspartic protease gene family during rapid growth of moso bamboo (Phyllostachys edulis) shoots

BACKGROUND

Aspartic proteases (APs) are a class of aspartic peptidases belonging to nine proteolytic enzyme families whose members are widely distributed in biological organisms. APs play essential functions during plant development and environmental adaptation. However, there are few reports about APs in fast-growing moso bamboo.

RESULT

In this study, we identified a total of 129 AP proteins (PhAPs) encoded by the moso bamboo genome. Phylogenetic and gene structure analyses showed that these 129 PhAPs could be divided into three categories (categories A, B and C). The PhAP gene family in moso bamboo may have undergone gene expansion, especially the members of categories A and B, although homologs of some members in category C have been lost. The chromosomal location of PhAPs suggested that segmental and tandem duplication events were critical for PhAP gene expansion. Promoter analysis revealed that PhAPs in moso bamboo may be involved in plant development and responses to environmental stress. Furthermore, PhAPs showed tissue-specific expression patterns and may play important roles in rapid growth, including programmed cell death, cell division and elongation, by integrating environmental signals such as light and gibberellin signals.

CONCLUSION

Comprehensive analysis of the AP gene family in moso bamboo suggests that PhAPs have experienced gene expansion that is distinct from that in rice and may play an important role in moso bamboo organ development and rapid growth. Our results provide a direction and lay a foundation for further analysis of plant AP genes to clarify their function during rapid growth.