Genome-wide identification of the pectate lyase(PEL)gene family members in Malvaceae,and their contribution to cotton fiber quality

Pectin is a major constituent of the plant cell wall.Pectate lyase(PEL,EC 4.2.2.2)uses anti-β-elimination chemistry to cleave theα-1,4 glycosidic linkage in the homogalacturonan region of pectin.However,limited information is available on the comprehensive and evolutionary analysis of PELs in the Malvaceae.In this study,we identified 597PEL genes from 10 Malvaceae species.Phylogenetic and motif analyses revealed that these PELs are classified into six subfamilies:Clades I,II,III,IV,Va,and Vb.The two largest subfamilies,Clades I and II,contained 237 and222 PEL members,respectively.The members of Clades Va and Vb only contained four or five motifs,far fewer than the other subfamilies.Gene duplication analysis showed that segmental duplication played a crucial role in the expansion of the PEL gene family in Gossypium species.The PELs from Clades I,IV,Va,and Vb were expressed during the fiber elongation stage,but nearly all PEL genes from Clades II and III showed no expression in any of the investigated fiber developmental stages.We further performed single-gene haplotype association analysis in 2,001G.hirsutum accessions and 229 G.barbadense accessions.Interestingly,14 PELs were significantly associated with fiber length and strength traits in G.barbadense with superior fiber quality,while only eight GhPEL genes were found to be significantly associated with fiber quality traits in G.hirsutum.Our findings provide important information for further evolutionary and functional research on the PEL gene family members and their potential use for fiber quality improvement in cotton.

High-quality genomes of Bombax ceiba and Ceiba pentandra provide insights into the evolution of Malvaceae species and differences in their natural fiber development

Members of the Malvaceae family,including Corchorus spp.,Gossypium spp.,Bombax spp.,and Ceiba spp.,are important sources of naturalfibers.In the past decade,the genomes of several Malvaceae species have been assembled;however,the evolutionary history of Malvaceae species and the differences in theirfiber development remain to be clarified.Here,we report the genome assembly and annotation of two nat-uralfiber plants from the Malvaceae,Bombax ceiba and Ceiba pentandra,whose assembled genome sizes are 783.56 Mb and 1575.47 Mb,respectively.Comparative analysis revealed that whole-genome duplication and Gypsy long terminal repeat retroelements have been the major causes of differences in chromosome number(2n=14 to 2n=96)and genome size(234 Mb to 2676 Mb)among Malvaceae species.We also used comparative genomic analyses to reconstruct the ancestral Malvaceae karyotype with 11 proto-chromo-somes,providing new insights into the evolutionary trajectories of Malvaceae species.MYB-MIXTA-like 3 is relatively conserved among the Malvaceae and functions infiber cell-fate determination in the epidermis.It appears to perform this function in any tissue where it is expressed,i.e.infibers on the endo-carp of B.ceiba and in ovulefibers of cotton.We identified a structural variation in a cellulose synthase gene and a higher copy number of cellulose synthase-like genes as possible causes of thefiner,less spinnable,weakerfibers of B.ceiba.Our study provides two high-quality genomes of naturalfiber plants and offers insights into the evolution of Malvaceae species and differences in their naturalfiber formation and devel-opment through multi-omics analysis.

Genomic insights into the genetic basis of cotton breeding in China

The excellent Upland cotton(Gossypium hirsutum)cultivars developed since 1949 have made a huge contribution to cotton production in China,the world's largest producer and consumer of cotton.However,the genetic and genomic basis for the improvements of these cotton cultivars remains largely unclear.In this study,we selected 16 Upland cotton cultivars with important historical status in Chinese cotton breeding and constructed a multiparent,advanced generation,intercross(MAGiC)population comprising 920 recombinant inbred lines.A genome-wide association study using the MAGIC population identified 54 genomic loci associated with lint yield and fiber quality.Of them,25(46.30%)pleiotropic genomic loci cause simultaneous changes of lint yield and/or fiber quality traits,revealing complex trade-offs and linkage drags in Upland cotton agronomic traits.Deep sequencing data of 11 introduced ancestor cultivars and publicly available resequencing datasets of 839 cultivars developed in China during the past 70 years were integrated to explore the historical distribution and origin of the elite or selected alleles.Interestingly,85%oftheseelitealleles were selectedandfixed fromdifferent Americanancestors,consistentwithcotton breeding practices in China.However,seven elite alleles of native origin that are responsible for Fusarium wilt resistance,early maturing,good-quality fiber,and other characteristics were not found in American an-cestors but have greatly contributed to Chinese cotton breeding and wide cultivation.Taken together,these results provide a genetic basis for further improving cotton cultivars and reveal that the genetic composition of Chinese cotton cultivars is narrow and mainly derived from early introduced American varieties.

UDP-glucosyltransferase 71C4 controls the flux of phenylpropanoid metabolism to shape cotton seed development

Seeds play a crucial role in plant reproduction,making it essential to identify genes that affect seed development.In this study,we focused on UDP-glucosyltransferase 71C4(UGT71C4)in cotton,a member of the glycosyltransferase family that shapes seed width and length,thereby influencing seed index and seed cotton yield.Overexpression of UGT71C4 results in seed enlargement owing to its glycosyltransferase activity on flavonoids,which redirects metabolic flux from lignin to flavonoid metabolism.This shift promotes cell proliferation in the ovule via accumulation of flavonoid glycosides,significantly enhancing seed cotton yield and increasing the seed index from 10.66 g to 11.91 g.By contrast,knockout of UGT71C4 leads to smaller seeds through activation of the lignin metabolism pathway and redirection of metabolic flux back to lignin synthesis.This redirection leads to increased ectopic lignin deposition in the ovule,inhibiting ovule growth and development,and alters yield components,increasing the lint percentage from 41.42%to 43.40%and reducing the seed index from 10.66 g to 8.60 g.Our research sheds new light on seed size development and reveals potential pathways for enhancing seed yield.

A new model system for cotton indoor genetic and genomic research

Dear Editor,As an important fiber and oil crop,cotton has gradually developed into a model plant for studying fiber or seed trichome and polyploid evolution.Thus,strengthening cotton research is essential.Significant progress has been made in the research of cotton genomics(Hu et al.,2019;Huang and Zhu,2021;Wen et al.,2022).However,further research has been hindered due to its long growth period(usually 4–6 months per generation)and large plant size(usually 0.8–1.5 m in height).

Underground communication:Long non-coding RNA signaling in the plant rhizosphere

Long non-coding RNAs(lncRNAs)have emerged as integral gene-expression regulators underlying plant growth,development,and adaptation.To adapt to the heterogeneous and dynamic rhizosphere,plants use interconnected regulatory mechanisms to optimally fine-tune gene-expression-governing interactions with soil biota,as well as nutrient acquisition and heavy metal tolerance.Recently,high-throughput sequencing has enabled the identification of plant lncRNAs responsive to rhizosphere biotic and abiotic cues.Here,we examine lncRNA biogenesis,classification,and mode of action,highlighting the functions of lncRNAs in mediating plant adaptation to diverse rhizosphere factors.We then discuss studies that reveal the significance and target genes of lncRNAs during developmental plasticity and stress responses at the rhizobium interface.A comprehensive understanding of specific lncRNAs,their regulatory targets,and the intricacies of their functional interaction networks will provide crucial insights into how these transcriptomic switches fine-tune responses to shifting rhizosphere signals.Looking ahead,we foresee that single-cell dissection of cell-type-specific lncRNA regulatory dynamics will enhance our understanding of the precise developmental modulation mechanisms that enable plant rhizosphere adaptation.Overcoming future challenges through multi-omics and genetic approaches will more fully reveal the integral roles of lncRNAs in governing plant adaptation to the belowground environment.

Nuclear translocation of OsMFT1 that is impeded by OsFTIP1 promotes drought toleranee in rice

Drought is the leading environmental threat affecting crop productivity,and plants have evolved a series of mechanisms to adapt to drought stress.The FT-interacting proteins(FTIPs)and phosphatidylethanola mine.binding proteins(PEBPs)play key roles in developmental processes,whereas their roles in the regulation of stress response are still largely unknown.Here,we report that OsFTIP1 negatively regulates drought response in rice.We showed that OsFTIP1 interacts with rice MOTHER OF FT AND TFL1(OsMFT1),a PEBP that promotes rice tolerance to drought treatment.Further studies discovered that OsMFT1 interacts with two key drought-related transcription factors,OsbZIP66 and OsMYB26,regulating their binding capacity on drought-related genes and thereby enhancing drought toleranee in rice.Interestingly,we found that OsFTIP1 impedes the nucleocytoplasmic translocation of OsMFT1,implying that dynamic modulation of drought-responsive genes by the OsMFT1-OsMYB26 and OsMFT1-OsbZIP66 complexes is integral to OsFTIP1-modulated nuclear accumulation of OsMFT1.Our findings also suggest that OsMFT1 might act as a hitherto unknown nucleocytoplasmic trafficking signal that regulates drought tolerance in rice in response to environmental signals.

Genome sequence of Gossypium anomalum facilitates interspecific introgression breeding

Crop wild relatives are an important reservoir of natural biodiversity. However, incorporating wild geneticdiversity into breeding programs is often hampered by reproductive barriers and a lack of accurate genomicinformation. We assembled a high-quality, accurately centromere-anchored genome of Gossypium anomalum, a stress-tolerant wild cotton species. We provided a strategy to discover and transfer agronomicallyvaluable genes from wild diploid species to tetraploid cotton cultivars. With a (Gossypium hirsutum 3 G.anomalum)2 hexaploid as a bridge parent, we developed a set of 74 diploid chromosome segment substitution lines (CSSLs) of the wild cotton species G. anomalum in the G. hirsutum background. This set of CSSLsincluded 70 homozygous substitutions and four heterozygous substitutions, and it collectively containedabout 72.22% of the G. anomalum genome. Twenty-four quantitative trait loci associated with plant height,yield, and fiber qualities were detected on 15 substitution segments. Integrating the reference genome withagronomic trait evaluation of the CSSLs enabled location and cloning of two G. anomalum genes thatencode peroxiredoxin and putative callose synthase 8, respectively, conferring drought tolerance andimproving fiber strength. We have demonstrated the power of a high-quality wild-species reference genomefor identifying agronomically valuable alleles to facilitate interspecific introgression breeding in crops.

Protein ubiquitination in plant peroxisomes

Protein ubiquitination regulates diverse cellular processes in eukaryotic organisms,from growth and development to stress response.Proteins subjected to ubiquitination can be found in virtually all subcellular locations and organelles,including peroxisomes,singlemembrane and highly dynamic organelles ubiquitous in eukaryotes.Peroxisomes contain metabolic functions essential to plants and animals such as lipid catabolism,detoxification of reactive oxygen species(ROS),biosynthesis of vital hormones and cofactors,and photorespiration.Plant peroxisomes possess a complex proteome with functions varying among different tissue types and developmental stages,and during plant response to distinct environmental cues.However,how these diverse functions are regulated at the post-translational level is poorly understood,especially in plants.In this review,we summarized current knowledge of the involvement of protein ubiquitination in peroxisome protein import,remodeling,pexophagy,and metabolism,focusing on plants,and referencing discoveries from other eukaryotic systems when relevant.Based on previous ubiquitinomics studies,we compiled a list of 56 ubiquitinated Arabidopsis peroxisomal proteins whose functions are associated with all the major plant peroxisomal metabolic pathways.This discovery suggests a broad impact of protein ubiquitination on plant peroxisome functions,therefore substantiating the need to investigate this significant regulatory mechanism in peroxisomes at more depths.

The OsFTIP6-OsHB22-OsMYBR57 module regulates drought response in rice

Plants have evolved a sophisticated set of mechanisms to adapt to drought stress.Transcription factors play crucial roles in plant responses to various environmental stimuli by modulating the expression of numerous stress-responsive genes.However,how the crosstalk between different transcription factor families orchestrates initiation of the key transcriptional network and the role of posttranscriptional modification of transcription factors,especially in cellular localization/trafficking in response to stress in rice,remain still largely unknown.In this study,we isolated an Osmybr57 mutant that displays a drought-sensitive phenotype through a genetic screen for drought stress sensitivity.We found that OsMYBR57,an MYB-related protein,directly regulates the expression of several key drought-related OsbZ/Ps in response to drought treatment.Further studies revealed that OsMYBR57 interacts with a homeodomain transcription factor,OsHB22,which also plays a positive role in drought signaling.We further demonstrate that OsFTIP6 interacts with OsHB22 and promotes the nucleocytoplasmic translocation of OsHB22 into the nucleus,where OsHB22 cooperates with OsMYBR57 to regulate the expression of drought-responsive genes.Our findings have revealed a mechanistic framework underlying the OsFTIP6-0sHB22-0sMYBR57 module-mediated regulation of drought response in rice.The OsFTIP6-mediated OsHB22 nucleocytoplasmic shuttling and OsMYBR57-0sHB22 regulation of OsbZIP transcription ensure precise control of expression of OsLEA3 and Rab21,and thereby regulate the response to water deficiency in rice.