Domestic Cotton Research Articles

Precise fine-turning of GhTFL1 by base editing tools defines ideal cotton plant architecture

BackgroundCRISPR/Cas-derived base editor enables precise editing of target sites and has been widely used for basic research and crop genetic improvement. However, the editing efficiency of base editors at different targets varies greatly.ResultsHere, we develop a set of highly efficient base editors in cotton plants. GhABE8e, which is fused to conventional nCas9, exhibits 99.9% editing efficiency, compared to GhABE7.10 with 64.9%, and no off-target editing is detected. We further replace nCas9 with dCpf1, which recognizes TTTV PAM sequences, to broaden the range of the target site. To explore the functional divergence of TERMINAL FLOWER 1 (TFL1), we edit the non-coding and coding regions of GhTFL1 with 26 targets to generate a comprehensive allelic population including 300 independent lines in cotton. This allows hidden pleiotropic roles for GhTFL1 to be revealed and allows us to rapidly achieve directed domestication of cotton and create ideotype germplasm with moderate height, shortened fruiting branches, compact plant, and early-flowering. Further, by exploring the molecular mechanism of the GhTFL1L86P and GhTFL1K53G+S78G mutations, we find that the GhTFL1L86P mutation weakens the binding strength of the GhTFL1 to other proteins but does not lead to a complete loss of GhTFL1 function.ConclusionsThis strategy provides an important technical platform and genetic information for the study and creation of ideal plant architecture.

Histone Maps in Gossypium darwinii Reveal Epigenetic Regulation Drives Subgenome Divergence and Cotton Domestication.

The functional annotation of genomes, including chromatin modifications, is essential to understand the intricate architecture of chromatin and the consequential gene regulation. However, such an annotation remains limited for cotton genomes. Here, we conducted chromatin profiling in a wild allotetraploid cotton Gossypium darwinii (AD genome) by integrating the data of histone modification, transcriptome, and chromatin accessibility. We revealed that the A subgenome showed a higher level of active histone marks and lower level of repressive histone marks than the D subgenome, which was consistent with the expression bias between the two subgenomes. We show that the bias in transcription and histone modification between the A and D subgenomes may be caused by genes unique to the subgenome but not by homoeologous genes. Moreover, we integrate histone marks and open chromatin to define six chromatin states (S1-S6) across the cotton genome, which index different genomic elements including genes, promoters, and transposons, implying distinct biological functions. In comparison to the domesticated cotton species, we observed that 23.2% of genes in the genome exhibit a transition from one chromatin state to another at their promoter. Strikingly, the S2 (devoid of epigenetic marks) to S3 (enriched for the mark of open chromatin) was the largest transition group. These transitions occurred simultaneously with changes in gene expression, which were significantly associated with several domesticated traits in cotton. Collectively, our study provides a useful epigenetic resource for research on allopolyploid plants. The domestication-induced chromatin dynamics and associated genes identified here will aid epigenetic engineering, improving polyploid crops.

Gossypium purpurascens genome provides insight into the origin and domestication of upland cotton

IntroductionAllotetraploid upland cotton (Gossypium hirsutum L.) is native to the Mesoamerican and Caribbean regions, had been improved in the southern United States by the mid-eighteenth century, was then dispersed worldwide. However, a Hainan Island Native Cotton (HIC) has long been grown extensively on Hainan Island, China. ObjectivesExplore HIC’s evolutionary relationship and genomic diversity with other tetraploid cottons, its origin and whether it was used for YAZHOUBU (Yazhou cloth, World Intangible Cultural Heritage) weaving, and the role of structural variations (SVs) in upland cotton domestication. MethodsWe assembled a high-quality genome of one HIC plant. We performed phylogenetic analysis, divergence time estimation, principal component analysis and population differentiation estimation using cotton assemblies and/or resequencing data. SVs were detected by whole-genome comparison. A F2 population was used for linkage analysis and to study effects of SVs. Buoyancy and salt water tolerance tests for seeds were conducted. ResultsWe found that the HIC belongs to G. purpurascens. G. purpurascens is best classified as a primitive race of G. hirsutum. The potential for long range transoceanic dispersal of G. purpurascens seeds was proved. A set of SVs, selective sweep regions between G. hirsutum races and cultivars, and quantitative trait loci (QTLs) of eleven agronomic traits were obtained. SVs, especially large-scale SVs, were found to have important effects on cotton domestication and improvement. Of them, eight large-scale inversions strongly associated with yield and fiber quality have probably undergone artificial selection in domestication. ConclusionG. purpurascens including HIC is a primitive race of G. hirsutum, probably disperse to Hainan from Central America by floating on ocean currents, may have been partly domesticated, planted and was likely used for YAZHOUBU weaving in Hainan much earlier than the Pre-Columbian period. SV plays an important role in cotton domestication and improvement.

Multiple domestication events explain the origin of Gossypium hirsutum landraces in Mexico.

Several Mesoamerican crops constitute wild-to-domesticated complexes generated by multiple initial domestication events, and continuous gene flow among crop populations and between these populations and their wild relatives. It has been suggested that the domestication of cotton (Gossypium hirsutum) started in the northwest of the Yucatán Peninsula, from where it spread to other regions inside and outside of Mexico. We tested this hypothesis by assembling chloroplast genomes of 23 wild, landraces, and breeding lines (transgene-introgressed and conventional). The phylogenetic analysis showed that the evolutionary history of cotton in Mexico involves multiple events of introgression and genetic divergence. From this, we conclude that Mexican landraces arose from multiple wild populations. Our results also revealed that their structural and functional chloroplast organizations had been preserved. However, genetic diversity decreases as a consequence of domestication, mainly in transgene-introgressed (TI) individuals (π=0.00020, 0.00001, 0.00016, 0, and 0, of wild, TI-wild, landraces, TI-landraces, and breeding lines, respectively). We identified homologous regions that differentiate wild from domesticated plants and indicate a relationship among the samples. A decrease in genetic diversity associated with transgene introgression in cotton was identified for the first time, and our outcomes are therefore relevant to both biosecurity and agrobiodiversity conservation.

The effect of shift in physiological and anatomical traits on light use efficiency under cotton domestication.

The effect of crop domestication on photosynthetic productivity has been well-studied, but at present, none examines its impacts on leaf anatomy and, consequently, light use efficiency in cotton. We investigated leaf and vein anatomy traits, light use efficiency (LUE) and gas exchange in 26 wild and 30 domesticated genotypes of cotton grown under field conditions. The results showed that domestication resulted in a higher photosynthetic rate, higher stomatal conductance, and lower lamina mass per area. Higher LUE was underpinned by the thicker leaves, greater vein volume, elongated palisade and higher chlorophyll content, although there was no difference in the apparent quantum yield. The lower vein mass per area in domesticated genotypes contributed to the reduction of lamina mass per area, but there was no decrease in vein length per area. Our study suggests that domestication has triggered a considerable shift in physiological and anatomical traits to support the increase in LUE.

The Transmission Effect Test of China’s Rotation Mechanism on the Cotton Reserve Market

As an important strategic material in China, cotton policy has positive significance in stabilizing the safety of domestic cotton, ensuring cotton income, and stabilizing cotton output. At the same time, affected by the future market price, the cotton industry supply chain cost management is particularly important. Based on the data of China’s cotton price, consumption, yield, and wheeling-in and wheeling-out from 1978 to 2016, the simultaneous equation model is used to empirically analyze the transmission effect of the rotation mechanism of reserve cotton (RMRC) on cotton supply and demand. Studies have shown that China’s cotton reserve policy and the RMRC play a positive role in balancing the supply and demand of the domestic cotton market and preventing excessive fluctuations in cotton prices. The transmission effect of the RMRC on domestic cotton yield and consumption is significant and there are certain differences. The transmission effect of domestic cotton yield is stronger than the transmission effect on domestic cotton consumption. The difference is owing to the transfer path of the RMRC being different. We should improve the regulation and control effect of the RMRC on cotton demand, realize the normalization of the RMRC, and clarify the policy objectives of the RMRC.

Genome and haplotype provide insights into the population differentiation and breeding improvement of Gossypium barbadense

IntroductionSea-island cotton (Gossypium barbadense, Gb) is one of the major sources of high-grade natural fiber. Besides the common annual Gb cotton, perennial Gb cotton is also cultivated, but studies on perennial Gb cotton are rare. ObjectivesWe aimed to make a systematic analysis of perennial sea-island cotton and lay a foundation for its utilization in breeding, and try to identify the representative structural variations (SVs) in sea-island cotton, and to reveal the population differentiation and adaptive improvement of sea-island cotton. MethodsThrough genome assembly of one perennial Gb cotton accession (named Gb_M210936) and comparative genome analysis, variations during Gb cotton domestication were identified by comparing Gb_M210936 with annual Gb accession 3–79 and with wild allotetraploid cotton G. darwinii. Six perennial Gb accessions combining with the resequenced 1,129 cotton accessions were used to conduct population and genetic analysis. Large haplotype blocks (haploblocks), generated from interspecific introgressions and intraspecific inversions, were identified and were used to analyze their effects on population differentiation and agronomic traits of sea-island cotton. ResultsOne reference genome of perennial sea-island cotton was assembled. Representative SVs in sea-island cotton were identified, and 31 SVs were found to be associated with agronomic traits. Perennial Gb cotton had a closer kinship with the wild-to-landrace continuum Gb cotton from south America where Gb cotton is originally domesticated. Haploblocks were associated with agronomic traits improvement of sea-island cotton, promoted sea-island cotton differentiation into three subgroups, were suffered from breeding selection, and may drive Gb cotton to be adapted to central Asian. ConclusionOur study made up the lack of perennial Gb cotton genome, and clarified that exotic introgressions improved the traits of sea-island cotton, promoted the population differentiation, and drove sea-island cotton adaptive to central Asia, which will provide new insights for the genetic breeding improvement of sea-island cottons.

Evolution of the Cotton Genus, Gossypium, and Its Domestication in the Americas

Gossypium, the cotton genus, includes ∼50 species distributed in tropical and sub-tropical regions of all continents except Europe. Here we provide a synopsis of the evolutionary history of Gossypium and domestication of the American allopolyploid species, integrating data from fundamental taxonomic investigations, biogeography, molecular genetics, phylogenetic analysis, and archaeology. These diverse sources of information provide a temporal and phylogenetic perspective on diversification among the diploids and on polyploid formation, uncover multiple previously cryptic interspecific hybridizations, clarify and contribute to the taxonomy of the genus, and offer a firm foundation for understanding parallel domestications in Mesoamerica and South America, which led to the globally important cotton crop species G. barbadense and G. hirsutum. Gossypium thus offers a testimonial example of the importance and utility of fundamental botanical discovery combined with modern technological capabilities to generate genomic insights into evolutionary history. We also review the current state of our knowledge regarding the archaeological history of cotton domestication and diffusion in the Americas, a seemingly unlikely story entailing parallel domestication origins and parallel directional selection tracing to 8,000 (G. barbadense) and 5,500 (G. hirsutum) years ago, transforming two geographically isolated wild short-day perennial shrubs having small capsules and seeds covered by short, tan-colored epidermal trichomes into modern daylength-neutral annuals bearing abundant, fine, strong white fibers. This dual domestication was followed several millennia later by unintentional and more recently intentional interspecific introgression, as the two species came into contact following their initial domestication in different hemispheres. Thus, the cycle of species divergence and biological reunion was reiterated, this time at the allopolyploid level. Understanding this evolutionary history is vitally important to our understanding of the genomic architecture of the world’s most important fiber plant and contributes substantially to our understanding of general biological principles.

The current state and level of development of the production forces of cotton and textile clusters

The article summarizes scientific and theoretical views on the characteristics and features of the formation of cotton cluster systems, briefly highlights the history of their appearance in Uzbekistan, the significance and consequences of clustering of the domestic cotton and textile industry, highlights the advantages and problems of introducing cotton and textile clusters into the agricultural production of Uzbekistan.

Long non-coding RNA and microRNA landscape of two major domesticated cotton species

Allotetraploid cotton plants Gossypium hirsutum and Gossypium barbadense have been widely cultivated for their natural, renewable textile fibres. Even though ncRNAs in domesticated cotton species have been extensively studied, systematic identification and annotation of lncRNAs and miRNAs expressed in various tissues and developmental stages under various biological contexts are limited. This influences the comprehension of their functions and future research on these cotton species. Here, we report high confidence lncRNAs and miRNA collection from G. hirsutum accession and G. barbadense accession using large-scale RNA-seq and small RNA-seq datasets incorporated into a user-friendly database, CoNCRAtlas. This database provides a wide range and depth of lncRNA and miRNA annotation based on the systematic integration of extensive annotations such as expression patterns derived from transcriptome data analysis in thousands of samples, as well as multi-omics annotations. We assume this comprehensive resource will accelerate evolutionary and functional studies in ncRNAs and inform future breeding programs for cotton improvement. CoNCRAtlas is accessible at http://www.nipgr.ac.in/CoNCRAtlas/.

개혁개방 이전 중국 면방직산업의 대외거래 연구

This paper aims to confirm how China's representative industry, the cotton textile industry, was influenced by external transactions before the reform and open door era, and what role it played in the Chinese economy.
 In the China’s cotton textile industry, raw cotton showed a significant level of self-sufficiency through domestic cotton cultivation. This result was because the Chinese government effectively implemented a cotton production increase policy through the planned economic system.
 In addition, few imports were made because cotton products were produced enough to meet domestic demand. Rather, by exporting cotton products that exceed domestic demand, food and facilities could be imported as export price.
 As a result, the China’s cotton textile industry has become a leading export industry. It contributed to economic growth by acquiring foreign currency through the export of cotton products and helping to solve the problem of foreign currency shortage in the early stages of economic development.
 Compared to the case of Korea, Korea and China showed different patterns in the external trade of raw cotton and cotton products, but their roles in the economy were similar.
 In conclusion, the China’s cotton textile industry increased production by importing raw cotton, which was insufficient through external transactions, and it can be said that it contributed to the development of the cotton textile industry and the development of the Chinese economy by exporting cotton products.

The earliest cotton fibers and Pan-regional contacts in the Near East.

Fiber technology (cordage and textile) has played a central role in all human societies for thousands of years, and its production, application and exchange have deep roots in prehistory. However, fiber remains have only rarely been observed in prehistoric sites because they tend to decay quickly in normal environmental conditions. To overcome preservation problems of macroscopic remains, we employed microbotanical analysis on soils from anthropogenic sediments in activity areas at Tel Tsaf in the Jordan Valley, Israel (ca. 5,200-4,700 cal BC), and recovered fiber microremains. This includes at least two types of bast fibers and the earliest evidence of cotton in the Near East, some of which were dyed in various colors. Some of these fibers likely represent the remnants of ancient clothing, fabric containers, cordage, or other belongings. The cotton remains, probably derived from wild species originating in South Asia, predate the oldest known cotton domestication in the Indus Valley by about two millennia. Tel Tsaf played a pivotal role in trans-regional trade and exchange networks in the southern Levant, and the presence of cotton at the site points to possible connections with the Indus Valley as early as 7,200 years ago.

The Gossypium herbaceum L. Wagad genome as a resource for understanding cotton domestication.

Gossypium herbaceum is a species of cotton native to Africa and Asia that is one of the 2 domesticated diploids. Together with its sister-species G. arboreum, these A-genome taxa represent models of the extinct A-genome donor of modern polyploid cotton, which provide about 95% of cotton grown worldwide. As part of a larger effort to characterize variation and improve resources among diverse diploid and polyploid cotton genomes, we sequenced and assembled the genome of G. herbaceum cultivar (cv.) Wagad, representing the first domesticated accession for this species. This chromosome-level genome was generated using a combination of PacBio long-read technology, HiC, and Bionano optical mapping and compared to existing genome sequences in cotton. We compare the genome of this cultivar to the existing genome of wild G. herbaceum subspecies africanum to elucidate changes in the G. herbaceum genome concomitant with domestication and extend these analyses to gene expression using available RNA-seq. Our results demonstrate the utility of the G. herbaceum cv. Wagad genome in understanding domestication in the diploid species, which could inform modern breeding programs.

Domestication has reduced leaf water use efficiency associated with the anatomy of abaxial stomata in cotton.

Crop domestication for increasing growth rates and yields appears to have altered the features of adaxial and abaxial stomata, but its effect on leaf water use efficiency (WUE) have not been experimentally verified. In this study, we characterized stomatal anatomy and carbon isotope discrimination (δ13C) in 32 wild and 36 domesticated genotypes of cotton grown under agricultural field conditions. The results showed that domesticated genotypes possessed lower WUE, as indicated by low or more negative δ13C compared with wild genotypes. Higher theoretical maximum stomatal conductance (gsmax) after domestication was accounted for by more stomata rather than significantly enlarged stomata. Specifically, abaxial stomatal density was higher whilst there was no change in the adaxial density. The size of both adaxial and abaxial stomata was greater due to larger guard cells but without there being any increase in pore size. However, there was a negative relationship between δ13C and stomatal size across wild and domesticated genotypes, especially on the abaxial leaf surface, because bigger stomata resulted in a lower maximum stomatal response rate to fluctuating canopy light, resulting in increased water loss. Overall, our results indicate that cotton domestication has resulted in substantial variation in stomatal anatomy, and that WUE and drought tolerance can potentially be improved in future breeding by decreasing the size of abaxial stomata to produce a faster stomatal response and hence a reduction in unnecessary water loss.

Evolutionary divergence of duplicated genomes in newly described allotetraploid cottons

Allotetraploid cotton (Gossypium) species represents a model system for the study of plant polyploidy, molecular evolution, and domestication. Here, chromosome-scale genome sequences were obtained and assembled for two recently described wild species of tetraploid cotton, Gossypium ekmanianum [(AD)6, Ge] and Gossypium stephensii [(AD)7, Gs], and one early form of domesticated Gossypium hirsutum, race punctatum [(AD)1, Ghp]. Based on phylogenomic analysis, we provide a dated whole-genome level perspective for the evolution of the tetraploid Gossypium clade and resolved the evolutionary relationships of Gs, Ge, and domesticated G. hirsutum. We describe genomic structural variation that arose during Gossypium evolution and describe its correlates-including phenotypic differentiation, genetic isolation, and genetic convergence-that contributed to cotton biodiversity and cotton domestication. Presence/absence variation is prominent in causing cotton genomic structural variations. A presence/absence variation-derived gene encoding a phosphopeptide-binding protein is implicated in increasing fiber length during cotton domestication. The relatively unimproved Ghp offers the potential for gene discovery related to adaptation to environmental challenges. Expanded gene families enoyl-CoA δ isomerase 3 and RAP2-7 may have contributed to abiotic stress tolerance, possibly by targeting plant hormone-associated biochemical pathways. Our results generate a genomic context for a better understanding of cotton evolution and for agriculture.

Leaf trait covariation and controls on leaf mass per area (LMA) following cotton domestication.

The process of domestication has driven dramatic shifts in plant functional traits, including leaf mass per area (LMA). It remains unclear whether domestication has produced concerted shifts in the lower-level anatomical traits that underpin LMA and how these traits in turn affect photosynthesis. In this study we investigated controls of LMA and leaf gas exchange by leaf anatomical properties at the cellular, tissue and whole-leaf levels, comparing 26 wild and 31 domesticated genotypes of cotton (Gossypium). As expected, domesticated plants expressed lower LMA, higher photosynthesis and higher stomatal conductance, suggesting a shift towards the 'faster' end of the leaf economics spectrum. At whole-leaf level, variation in LMA was predominantly determined by leaf density (LD) both in wild and domesticated genotypes. At tissue level, higher leaf volume per area (Vleaf) in domesticated genotypes was driven by a simultaneous increase in the volume of epidermal, mesophyll and vascular bundle tissue and airspace, while lower LD resulted from a lower volume of palisade tissue and vascular bundles (which are of high density), paired with a greater volume of epidermis and airspace, which are of low density. The volume of spongy mesophyll exerted direct control on photosynthesis in domesticated genotypes but only indirect control in wild genotypes. At cellular level, a shift to larger but less numerous cells with thinner cell walls underpinned a lower proportion of cell wall mass, and thus a reduction in LD. Taken together, cotton domestication has triggered synergistic shifts in the underlying determinants of LMA but also photosynthesis, at cell, tissue and whole-leaf levels, resulting in a marked shift in plant ecological strategy.

Conservation and Divergence of Phosphoenolpyruvate Carboxylase Gene Family in Cotton.

Phosphoenolpyruvate carboxylase (PEPC) is an important enzyme in plants, which regulates carbon flow through the TCA cycle and controls protein and oil biosynthesis. Although it is important, there is little research on PEPC in cotton, the most important fiber crop in the world. In this study, a total of 125 PEPCs were identified in 15 Gossypium genomes. All PEPC genes in cotton are divided into six groups and each group generally contains one PEPC member in each diploid cotton and two in each tetraploid cotton. This suggests that PEPC genes already existed in cotton before their divergence. There are additional PEPC sub-groups in other plant species, suggesting the different evolution and natural selection during different plant evolution. PEPC genes were independently evolved in each cotton sub-genome. During cotton domestication and evolution, certain PEPC genes were lost and new ones were born to face the new environmental changes and human being needs. The comprehensive analysis of collinearity events and selection pressure shows that genome-wide duplication and fragment duplication are the main methods for the expansion of the PEPC family, and they continue to undergo purification selection during the evolutionary process. PEPC genes were widely expressed with temporal and spatial patterns. The expression patterns of PEPC genes were similar in G. hirsutum and G. barbadense with a slight difference. PEPC2A and 2D were highly expressed in cotton reproductive tissues, including ovule and fiber at all tested developmental stages in both cultivated cottons. However, PEPC1A and 1D were dominantly expressed in vegetative tissues. Abiotic stress also induced the aberrant expression of PEPC genes, in which PEPC1 was induced by both chilling and salinity stresses while PEPC5 was induced by chilling and drought stresses. Each pair (A and D) of PEPC genes showed the similar response to cotton development and different abiotic stress, suggesting the similar function of these PEPCs no matter their origination from A or D sub-genome. However, some divergence was also observed among their origination, such as PEPC5D was induced but PEPC5A was inhibited in G. barbadense during drought treatment, suggesting that a different organized PEPC gene may evolve different functions during cotton evolution. During cotton polyploidization, the homologues genes may refunction and play different roles in different situations.

An InVitro Co-Culture System for Rapid Differential Response to Fusarium oxysporum f. sp. vasinfectum Race 4 in Three Cotton Cultivars.

Fusarium oxysporum f. sp. vasinfectum race 4 (FOV4) is a devastating fungus pathogen that causes Fusarium wilt in both domesticated cotton species, Gossypium hirsutum (Upland) and G. barbadense (Pima). Greenhouse and field-based pathogenicity assays can be a challenge because of nonuniform inoculum levels, the presence of endophytes, and varying environmental factors. Therefore, an invitro coculture system was designed to support the growth of both domesticated cotton species and FOV4 via an inert polyphenolic foam substrate with a liquid medium. A Fusarium wilt-susceptible Pima cotton cultivar, G. barbadense 'GB1031'; a highly resistant Pima cotton cultivar, G. barbadense 'DP348RF'; and a susceptible Upland cotton cultivar, G. hirsutum 'TM-1', were evaluated for 30 days during coculture with FOV4 in this foam-based system. Thirty days after inoculation, disease symptoms were more severe in both susceptible cultivars, which displayed higher percentages of foliar damage, and greater plant mortality than observed in 'DP348RF', the resistant Pima cotton cultivar. This foam-based invitro system may be useful for screening cotton germplasm for resistance to a variety of fungus pathogens and may facilitate the study of biotic interactions in domesticated cotton species under controlled environmental conditions.

Enhanced photosynthetic nitrogen use efficiency and increased nitrogen allocation to photosynthetic machinery under cotton domestication.

Domestication involves dramatic phenotypic and physiological diversifications due to successive selection by breeders toward high yield and quality. Although photosynthetic nitrogen use efficiency (PNUE) is a major trait for understanding leaf nitrogen economy, it is unclear whether PNUE of cotton has been improved under domestication. Here, we investigated the effect of domestication on nitrogen allocation to photosynthetic machinery and PNUE in 25 wild and 37 domesticated cotton genotypes. The results showed that domesticated genotypes had higher nitrogen content per mass (Nm), net photosynthesis under saturated light (Asat), and PNUE but similar nitrogen content per area (Na) compared with wild genotypes. As expected, in both genotypes, PNUE was positively related to Asat but negatively correlated with Na. However, the relative contribution of Asat to PNUE was greater than the contribution from Na. Domesticated genotypes had higher nitrogen allocation to light-harvesting (NL, nitrogen in light-harvesting chlorophyll-protein complex), to bioenergetics (Nb, total nitrogen of cytochrome f, ferredoxin NADP reductase, and the coupling factor), and to Rubisco (Nr) than wild genotypes; however, the two genotype groups did not differ in PNUEp, the ratio of Asat to Np (itself the sum of NL, Nb, and Nr). Our results suggest that more nitrogen allocation to photosynthetic machinery has boosted Asat under cotton domestication. Improving the efficiency of nitrogen use in photosynthetic machinery might be future aim to enhance Asat of cotton.

Comparisons of photosynthetic and anatomical traits between wild and domesticated cotton.

Mesophyll conductance (gm) is a crucial leaf trait contributing to the photosynthetic rate (AN). Plant domestication typically leads to an enhancement of AN that is often associated with profound anatomical modifications, but it is unclear which of these structural alterations influence gm. We analyzed the implication of domestication on leaf anatomy and its effect on gm in 26 wild and 31 domesticated cotton genotypes (Gossypium sp.) grown under field conditions. We found that domesticated genotypes had higher AN but similar gm to wild genotypes. Consistent with this, domestication did not translate into significant differences in the fraction of mesophyll occupied by intercellular air spaces (fias) or mesophyll and chloroplast surface area exposed to intercellular air space (Sm/S and Sc/S, respectively). However, leaves of domesticated genotypes were significantly thicker, with larger but fewer mesophyll cells with thinner cell walls. Moreover, domesticated genotypes had higher cell wall conductance (gcw) but smaller cytoplasmic conductance (gcyt) than wild genotypes. It appears that domestication in cotton has not generally led to significant improvement in gm, in part because their thinner mesophyll cell walls (increasing gcw) compensate for their lower gcyt, itself due to larger distance between plasmalemma and chloroplast envelopes.