Gene expression and metabolite profiles of cotton fiber during cell elongation and secondary cell wall synthesis

棉花纤维在延伸的开始以后很快伸长，最后导致大量纤维素的存款。为了在快延伸和第二等的细胞壁合成揭示棉花纤维房间的特征，上演，我们比较了 respectivetranscriptomes 和代谢物侧面。由 cDNA 数组的 transcriptomes 的比较分析识别了是在纤维开发期间调整的差别的 633 基因。用变量把纤维样品划分了成四的表示基因的 Principalcomponent 分析(PCA ) 组织，它发育阶段是诊断的。如果，类似的组织结果也被发现我们是的 usenon 极或极的代谢物为开发纤维的 PCA 的变量。植物生长素发信号，松开墙并且脂类代谢在纤维延伸期间是高度活跃的，而纤维素生合成是占优势的，许多另外的新陈代谢的小径是在第二等的细胞壁合成调整的 down，上演。抄本和代谢物侧面和酶活动在向纤维素合成表明棉花纤维开发的一个专门化过程是一致的。这些数据证明在某个阶段的那个棉花纤维房间有它棉花纤维房间的自己的唯一的特征，和发育阶段能被他们的抄本和代谢物侧面区分。在第二等的细胞壁合成阶段期间，新陈代谢的小径被流进纤维素合成。

Single-cell RNA sequencing reveals a hierarchical transcriptional regulatory network of terpenoid biosynthesis in cotton secretory glandular cells

Plants can synthesize a wide range of terpenoids in response to various environmental cues.However,the specific regulatory mechanisms governing terpenoid biosynthesis at the cellular level remain largely elusive.In this study,we employed single-cell RNA sequencing to comprehensively characterize the transcriptome profile of cotton leaves and established a hierarchical transcriptional network regulating cellspecific terpenoid production.We observed substantial expression levels of genes associated with the biosynthesis of both volatile terpenes(such asβ-caryophyllene andβ-myrcene)and non-volatile gossypol-type terpenoids in secretory glandular cells.Moreover,two novel transcription factors,namely GoHSFA4a and GoNAC42,are identified to function downstream of the Gossypium PIGMENT GLAND FORMATION genes.Both transcription factors could directly regulate the expression of terpenoid biosynthetic genes in secretory glandular cells in response to developmental and environmental stimuli.For convenient retrieval of the single-cell RNA sequencing data generated in this study,we developed a user-friendly web server.Our findings not only offer valuable insights into the precise regulation of terpenoid biosynthesis genes in cotton leaves but also provide potential targets for cotton breeding endeavors.

The Jasmonate-Responsive AP2/ERF Transcription Factors AaERF1 and AaERF2 Positively Regulate Artemisinin Biosynthesis in Artemisia annua L.

Plants of Artemisia annua produce artemisinin, a sesquiterpene lactone widely used in malaria treatment. Amorpha-4,11-diene synthase （ADS）, a sesquiterpene synthase, and CYP71AV1, a P450 monooxygenase, are two key enzymes of the artemisinin biosynthesis pathway. Accumulation of artemisinin can be induced by the phytohormone jasmonate （JA）. Here, we report the characterization of two JA-responsive AP2 family transcription factors-AaERF1 and AaERF2-from A. annua L. Both genes were highly expressed in inflorescences and strongly induced by JA. Yeast one- hybrid and electrophoretic mobility shift assay （EMSA） showed that they were able to bind to the CRTDREHVCBF2 （CBF2） and RAVlAAT （RAA） motifs present in both ADS and CYP71AV1 promoters. Transient expression of either AaERF1 or AaERF2 in tobacco induced the promoter activities of ADS or CYP71AV1, and the transgenic A. annua plants overexpressing either transcription factor showed elevated transcript levels of both ADS and CYP71AV1, resulting in increased accumulation of artemisinin and artemisinic acid. By contrast, the contents of these two metabolites were reduced in the RNAi transgenic lines in which expression of AaERF1 or AaERF2 was suppressed. These results demonstrate that AaERF1 and AaERF2 are two positive regulators of artemisinin biosynthesis and are of great value in genetic engineering of arte- misinin production.

Plant Terpenoids： Biosynthesis and Ecological Functions

Among plant secondary metabolites terpenolds are a structurally most diverse group; they function as phytoalexins In plant direct defense, or as signals In Indirect defense responses which involves herbivores and their natural enemies. In recent years, more and more attention has been paid to the Investigation of the ecological role of plant terpenolds. The biosynthesis pathways of monoterpenes, sesquiterpenes, and diterpenes Include the synthesis of C5 precursor isopentenyl diphosphate （IPP） and Its allylic isomer dlmethylallyl dlphosphate （DMAPP）, the synthesis of the immediate diphosphate precursors, and the formation of the diverse terpenoids. Terpene synthases （TPSs） play a key role In volatile terpene synthesis. By expression of the TPS genes, significant achievements have been made on metabolic engineering to Increase terpenoid production. This review mainly summarizes the recent research progress In elucidating the ecological role of terpenoids and characterization of the enzymes Involved in the terpenold biosynthesis. Spatial and temporal regulations of terpenoids metabolism are also discussed.

Transcriptional Regulation of Plant Secondary Metabolism

Plant secondary metabolites play critical roles in plant-environment interactions. They are synthesized in different organs or tissues at particular developmental stages, and in response to various environmental stimuli, both biotic and abiotic. Accordingly, corresponding genes are regulated at the transcriptional level by multiple transcription factors. Several families of transcription factors have been identified to participate in controlling the biosynthesis and accumulation of secondary metabolites. These regulators integrate internal （often developmental） and external signals, bind to corresponding cis-elements -- which are often in the promoter regions -- to activate or repress the expression of enzyme-coding genes, and some of them interact with other transcription factors to form a complex. In this review, we summarize recent research in these areas, with an emphasis on newly-identified transcription factors and their functions in metabolism regulation.

A Cotton BURP Domain Protein Interacts With α-Expansin and Their Co-Expression Promotes Plant Growth and Fruit Production

Plant growth requires cell wall extension. The cotton AtRD22-Like I gene GhRDL1, predominately expressed in elongating fiber cells, encodes a BURP domain-containing protein. Here, we show that GhRDL1 is localized in cell wall and interacts with GhEXPA1, an α-expansin functioning in wall loosening. Transgenic cotton overexpressing GhRDL1 showed an increase in fiber length and seed mass, and an enlargement of endopleura cells of ovules. Expression of either GhRDL1 or GhEXPA1 alone in Arabidopsis led to a substantial increase in seed size; interestingly, their co-expression resulted in the increased number of siliques, the nearly doubled seed mass, and the enhanced biomass production. Cotton plants overexpressing GhRDL1 and GhEXPA1 proteins produced strikingly more fruits （bolls）, leading to up to 40% higher fiber yield per plant without adverse effects on fiber quality and vegetative growth. We demonstrate that engineering cell wall protein partners has a great potential in promoting plant growth and crop yield.

The miR319-Targeted GhTCP4 Promotes the Transition from Cell Elongation to Wall Thickening in Cotton Fiber

Plant cell growth involves a complex interplay among cell-wall expansion, biosynthesis, and, in specific tissues, secondary cell wall (SCW) deposition, yet the coordination of these processes remains elusive. Cotton fiber cells are developmentally synchronous, highly elongated, and contain nearly pure cellulose when mature. Here, we report that the transcription factor GhTCP4 plays an important role in balancing cotton fiber cell elongation and wall synthesis. During fiber development the expression of miR319 declines while GhTCP4 transcript levels increase, with high levels of the latter promoting SCW deposition. GhTCP4 interacts with a homeobox-containing factor, GhHOX3, and repressing its transcriptional activity. GhTCP4 and GhHOX3 function antagonistically to regulate cell elongation, thereby establishing temporal control of fiber cell transition to the SCW stage. We found that overexpression of GhTCP4A upregulated and accelerated activation of the SCW biosynthetic pathway in fiber cells, as revealed by transcriptome and promoter activity analyses, resulting in shorter fibers with varied lengths and thicker walls. In contrast, GhTCP4 downregulation led to slightly longer fibers and thinner cell walls. The GhHOX3–GhTCP4 complex may represent a general mechanism of cellular development in plants since both are conserved factors in many species, thus providing us a potential molecular tool for the design of fiber traits.

Lipidomic Analysis Reveals the Importance of GIPCs in Arabidopsis Leaf Extracellular Vesicles

Plant extracellular vesicles(EVs)are membrane-enclosed nanoparticles that play diverse roles in plant development and response.Recently,impressive progress has been made in the isolation and identification of the proteins and RNAs carried in plant EVs;however,the analysis of EV lipid compositions remains rudimentary.Here,we performed lipidomic analysis of Arabidopsis rosette leaf EVs,revealing a high abundance of certain groups of lipids,in particular sphingolipids,in the EVs.Remarkably,the EV sphingolipids are composed of nearly pure glycosylinositolphosphoceramides(GIPCs),which are green lineage abundant and negatively charged.We further showed that the Arabidopsis TETRASPANIN 8(TET8)knockout mutant has a lower amount of cellular GIPCs and secrets fewer EVs,companied with impaired reactive oxygen species(ROS)burst toward stresses.Exogenous application of GIPCs promoted the secretion of EVs and ROS burst in both the WT and tet8 mutant.The characteristic enrichment of sphingolipid GIPCs provides valuable insights into the biogenesis and function of plant EVs.

Sphingolipid metabolism, transport, and functions in plants:Recent progress and future perspectives

Sphingolipids,which comprise membrane systems together with other lipids,are ubiquitous in cellular organisms.They show a high degree of diversity across plant species and vary in their structures,properties,and functions.Benefiting from the development of lipidomic techniques,over 300 plant sphingolipids have been identified.Generally divided into free long-chain bases(LCBs),ceramides,glycosylceramides(GlcCers)and glycosyl inositol phosphoceramides(GIPCs),plant sphingolipids exhibit organized aggregation within lipid membranes to form raft domains with sterols.Accumulating evidence has revealed that sphingolipids obey certain trafficking and distribution rules and confer unique properties to membranes.Functional studies using sphingolipid biosynthetic mutants demonstrate that sphingolipids participate in plant developmental regulation,stimulus sensing,and stress responses.Here,we present an updated metabolism/degradation map and summarize the structures of plant sphingolipids,review recent progress in understanding the functions of sphingolipids in plant development and stress responses,and review sphingolipid distribution and trafficking in plant cells.We also highlight some important challenges and issues that we may face during the process of studying sphingolipids.

RES transformation for biosynthesis and detoxification

The reactive electrophilic species(RES), typically the molecules bearing α,β-unsaturated carbonyl group, are widespread in living organisms and notoriously known for their damaging effects. Many of the mycotoxins released from phytopathogenic fungi are RES and their contamination to cereals threatens food safety worldwide. However, due to their high reactivity, RES are also used by host organisms to synthesize specific metabolites. The evolutionary conserved glyoxalase(GLX) system scavenges the cytotoxic α-oxoaldehydes that bear RES groups, which cause host disorders and diseases. In cotton, a specialized enzyme derived from glyoxalase I(GLXI) through gene duplications and named as specialized GLXI(SPG), acts as a distinct type of aromatase in the gossypol pathway to transform the RES intermediates into the phenolic products. In this review, we briefly introduce the research progress in understanding the RES, especially the RES-type mycotoxins, the GLX system and SPG, and discuss their application potential in detoxification and synthetic biology.

Cotton genome: challenge into the polyploidy

Cottons are the most important fiber crops in the world.The cotton genus Gossypium has 52 species,including seven allotetraploid species and 45 diploids.Four species were domesticated and remain as crops under cultivation today:the New World allopolyploid species G.hirsutum and G.barbadense(2n=52),and the Old World diploid species G.arboreum and G.herbaceum(2n=26).The primary cultivated species is Upland cotton(G.hirsutum L.),which accounts for more than 90%of global cotton fiber production.