T1 Locus Research Articles

Structure, biosynthesis and regulation of the T1 antigen, a phase-variable surface polysaccharide conserved in many Salmonella serovars

The bacterial genus Salmonella includes diverse isolates with multiple variations in the structure of the main polysaccharide component (O antigen) of membrane lipopolysaccharides. In addition, some isolates produce a transient (T) antigen, such as the T1 polysaccharide identified in the 1960s in an isolate of Salmonella enterica Paratyphi B. The structure and biosynthesis of the T1 antigen have remained enigmatic. Here, we use biophysical, biochemical and genetic methods to show that the T1 antigen is a complex linear glycan containing tandem homopolymeric domains of galactofuranose and ribofuranose, linked to lipid A–core, like a typical O antigen. T1 is a phase-variable antigen, regulated by recombinational inversion of the promoter upstream of the T1 genetic locus through a mechanism not observed for other bacterial O antigens. The T1 locus is conserved across many Salmonella isolates, but is mutated or absent in most typhoidal serovars and in serovar Enteritidis.

Safe-Harboring based novel genetic toolkit for Nannochloropsis salina CCMP1776: Efficient overexpression of transgene via CRISPR/Cas9-Mediated Knock-in at the transcriptional hotspot

Transgene expression in microalgae can be hampered by transgene silencing and unstable expression due to position effects. To overcome this, “safe harboring” transgene expression system was established for Nannochloropsis. Initially, transformants were obtained expressing a sfGFP reporter, followed by screening for high expression of sfGFP with fluorescence-activated cell sorter (FACS). 'T1' transcriptional hotspot was identified from a mutant showing best expression of sfGFP, but did not affect growth or lipid contents. By using a Cas9 editor strain, FAD12 gene, encoding Δ12-fatty acid desaturase (FAD12), was successfully knocked-in at the T1 locus, resulting in significantly higher expression of FAD12 than those of random integration. Importantly, the “safe harbored” FAD12 transformants showed four-fold higher production of linoleic acid (LA), the product of FAD12, leading to 1.5-fold increase in eicosapentaenoic acid (EPA). This safe harboring principle provide excellent proof of the concept for successful genetic/metabolic engineering of microalgae and other organisms.

Acetylcholinesterase, Butyrylcholinesterase and Glutathione S-Transferase Enzyme Activities and Their Correlation with Genotypic Variations Based on GST M1 and GST T1 Loci in Long Term-Pesticide-Exposed Tea Garden Workers of Sub-Himalayan West Bengal

Organophosphates (OPs) and carbamates (CBs) are known to reduce acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) and increase Glutathione S-Transferase (GST) activities in the exposed individuals. We have evaluated AChE, BChE and GST activities in long-term pesticide exposed tea garden workers of sub-Himalayan West Bengal and tried to relate enzyme activities with polymorphisms in GST M1 and GST T1 genes. Enzyme activities were measured spectro-photometrically in blood samples of sprayers and pluckers in relation to age-matched control individuals. Allele-specific multiplex-PCR was employed to score the presence of GST M1 and GST T1 alleles. Significantly lower (p < 0.01) level of AChE and BChE activities were found in the worker group (3.15 ± 0.69 µmol/min/mL of lysate and 1.2 ± 0.54 µmol/min/mL of plasma respectively) compared to the control group (3.74±0.26 µmol/min/mL of lysate and 2.21 ±0.27 µmol/min/mL of plasma respectively). Whereas, significantly higher (p < 0.01) level of GST activity was detected in the worker group (3.83 ±0.97 lU/gm of Hb) comprising of 61 individuals compared to control group (2.47 ±0.29 lU/gm of Hb) comprising of equal number of individuals. Out of total 122 individuals, 34.43% had both GST M1 and GST T1, 23.77% had single-null genotype for GST T1, 27.05% had the single-null genotype for GST M1 and 14.75% individuals had double-null genotypes. We found no significant difference in enzyme activities among the four genotypes when test and control groups were compared. This study for the first time explored changes in AChE, BChE and GST activities in tea garden workers exposed chronically to OPs and CBs in the studied region. Our study indicated that exposure to OP and CB pesticides leads to changes in AChE, BChE and GST activities and the presence or absence of GST M1 and GST T1 alleles are possibly not related to the changes in AChE, BChE and GST activities.

Up-regulation of a homeodomain-leucine zipper gene HD-1 contributes to trichome initiation and development in cotton

Plant trichomes originate from epidermal cells. In this work, we demonstrated that a homeodomain-leucine zipper (HD-Zip) gene, Gh_A06G1283 (GhHD-1A), was related to the leaf trichome trait in allotetraploid cotton and could be a candidate gene for the T1 locus. The ortholog of GhHD-1A in the hairless accession Gossypium barbadense cv. Hai7124 was interrupted by a long terminal repeat (LTR) retrotransposon, while GhHD-1A worked well in the hairy accession Gossypium hirsutum acc. T586. Sequence and phylogenetic analysis showed that GhHD-1A belonged to the HD-Zip IV gene family, which mainly regulated epidermis hair development in plants. Silencing of GhHD-1A and its homoeologs GhHD-1D in allotetraploid T586 and Hai7124 could significantly reduce the density of leaf hairs and affect the expression levels of other genes related to leaf trichome formation. Further analysis found that GhHD-1A mainly regulated trichome initiation on the upper epidermal hairs of leaves in cotton, while the up-regulated expression of GhHD-1A in different organs/tissues also altered epidermal trichome development. This study not only helps to unravel the important roles of GhHD-1A in regulating trichome initiation in cotton, but also provides a reference for exploring the different forms of trichome development in plants.

Association of ADAM33 gene polymorphisms with asthma in Mongolian and Han groups in Inner Mongolia.

Polymorphisms in the gene encoding for A disintegrin and metalloprotease 33 (ADAM33) are closely associated with the risk of bronchial asthma attacks in different populations. We collected blood samples from 248 asthma patients – 130 of the Han ethnic group and 118 of the Mongolian ethnic group – living in the Inner Mongolia region of China, and analyzed the single nuclear polymorphisms (SNPs) of the T1, T2 and V4 loci of the ADAM33 gene using PCR-RFLP (restriction fragment length polymorphism). In addition, we also tested 256 healthy controls (134 and 122 from the Han and Mongolian ethnic groups respectively) for the same SNPs. Three genotypes of the T1, T2 and V4 loci were predominantly detected: while polymorphisms in the T1 locus were significantly associated with asthma risk in both Mongolian and Han ethnicities (P < 0.05, ∗P < 0.05), that in the V4 locus were relevant only in the Mongolian patients (P < 0.05, ∗P > 0.05). In contrast, polymorphisms in the T2 locus showed no significant association with asthma risk in either ethnic group (P > 0.05, ∗P > 0.05).

Fine mapping and RNA-Seq unravels candidate genes for a major QTL controlling multiple fiber quality traits at the T1 region in upland cotton.

BackgroundImproving fiber quality is a major challenge in cotton breeding, since the molecular basis of fiber quality traits is poorly understood. Fine mapping and candidate gene prediction of quantitative trait loci (QTL) controlling cotton fiber quality traits can help to elucidate the molecular basis of fiber quality. In our previous studies, one major QTL controlling multiple fiber quality traits was identified near the T1 locus on chromosome 6 in Upland cotton.ResultsTo finely map this major QTL, the F2 population with 6975 individuals was established from a cross between Yumian 1 and a recombinant inbred line (RIL118) selected from a recombinant inbred line population (T586 × Yumian 1). The QTL was mapped to a 0.28-cM interval between markers HAU2119 and SWU2302. The QTL explained 54.7 % (LOD = 222.3), 40.5 % (LOD = 145.0), 50.0 % (LOD = 194.3) and 30.1 % (LOD = 100.4) of phenotypic variation with additive effects of 2.78, −0.43, 2.92 and 1.90 units for fiber length, micronaire, strength and uniformity, respectively. The QTL region corresponded to a 2.7-Mb interval on chromosome 10 in the G. raimondii genome sequence and a 5.3-Mb interval on chromosome A06 in G. hirsutum. The fiber of Yumian 1 was much longer than that of RIL118 from 3 DPA to 7 DPA. RNA-Seq of ovules at 0 DPA and fibers at 5 DPA from Yumian 1 and RIL118 showed four genes in the QTL region of the G. raimondii genome to be extremely differentially expressed. RT-PCR analysis showed three genes in the QTL region of the G. hirsutum genome to behave similarly.ConclusionsThis study mapped a major QTL influencing four fiber quality traits to a 0.28-cM interval and identified three candidate genes by RNA-Seq and RT-PCR analysis. Integration of fine mapping and RNA-Seq is a powerful strategy to uncover candidates for QTL in large genomes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-2605-6) contains supplementary material, which is available to authorized users.

The Hairless Stem Phenotype of Cotton (Gossypium barbadense) Is Linked to a Copia-Like Retrotransposon Insertion in a Homeodomain-Leucine Zipper Gene (HD1).

Cotton (Gossypium) stem trichomes are mostly single cells that arise from stem epidermal cells. In this study, a homeodomain-leucine zipper gene (HD1) was found to cosegregate with the dominant trichome locus previously designated as T1 and mapped to chromosome 6. Characterization of HD1 orthologs revealed that the absence of stem trichomes in modern Gossypium barbadense varieties is linked to a large retrotransposon insertion in the ninth exon, 2565 bp downstream from the initial codon in the At subgenome HD1 gene (At-GbHD1). In both the At and Dt subgenomes, reduced transcription of GbHD1 genes is caused by this insertion. The disruption of At-HD1 further affects the expression of downstream GbMYB25 and GbHOX3 genes. Analyses of primitive cultivated accessions identified another retrotransposon insertion event in the sixth exon of At-GbHD1 that might predate the previously identified retrotransposon in modern varieties. Although both retrotransposon insertions results in similar phenotypic changes, the timing of these two retrotransposon insertion events fits well with our current understanding of the history of cotton speciation and dispersal. Taken together, the results of genetics mapping, gene expression and association analyses suggest that GbHD1 is an important component that controls stem trichome development and is a promising candidate gene for the T1 locus. The interspecific phenotypic difference in stem trichome traits also may be attributable to HD1 inactivation associated with retrotransposon insertion.

Effect of interactions of glutathione S‐transferase T1, M1, and P1 and HMOX1 gene promoter polymorphisms with heavy smoking on the risk of rheumatoid arthritis

Glutathione S-transferase (GST) genes as well as heme oxygenase 1 gene (HMOX1) encode enzymes that detoxify carcinogens and protect against oxidative stress. This study was undertaken to examine the impact of gene-smoking interactions on susceptibility to rheumatoid arthritis (RA). Caucasian patients with RA and matched control subjects (n = 549 each) were selected from the Nurses' Health Study. Genotyping of the patients' blood by TaqMan and BioTrove assays identified homozygous deletions at the M1 and T1 loci of GST (GSTM1-null and GSTT1-null, respectively) as well as alleles for GSTP1 (rs1695) and HMOX1 (rs2071746). In addition, the effect of gene-smoking interactions on the risk of all RA and RA serologic phenotypes was studied in separate logistic models that were adjusted for covariates. Multiplicative interactions were assessed by including a product term in a logistic model, and additive interactions were assessed using the attributable proportion (AP) due to interaction. For replication of the results, analyses revealing significant interactions were repeated in an independent case-control cohort from the Epidemiological Investigation of Rheumatoid Arthritis study. For the risk of all RA, multiplicative (P = 0.05) and additive (AP = 0.53, P = 0.0005) interactions between the GSTT1-null polymorphism and smoking and multiplicative interactions (P = 0.05) between HMOX1 and smoking were observed. For the risk of seropositive RA, multiplicative (P = 0.01) and additive (AP = 0.62, P < 0.0001) interactions between GSTT1-null and smoking and additive interactions (AP = 0.41, P = 0.03) between HMOX1 and smoking were observed. After correction for multiple comparisons, the additive interactions between GSTT1-null and smoking remained significant. The M1-null and P1 variants of GST did not show significant interactions, and no associations with seronegative RA were observed. In replication analyses, significant multiplicative interactions (P = 0.04) and additive interactions (AP = 0.32, P = 0.02) were observed between GSTT1-null and smoking in the risk of anti-citrullinated protein antibody-positive RA. Significant gene-environment interactions between the GSTT1-null polymorphism and heavy smoking were observed when assessing the risk of RA. Future studies are needed to assess the impact of these interactions on RA prediction.

Correspondence of Trichome Mutations in Diploid and Tetraploid Cottons

Quantitative variation for leaf trichome number is observed within and among Gossypium species, varying from glabrous to densely pubescent phenotypes. Moreover, economically important cotton lint fibers are modified trichomes. Earlier studies have mapped quantitative trait loci (QTLs) affecting leaf pubescence in Gossypium using allotetraploids. In this study, we mapped genes responsible for leaf trichome density in a diploid A genome cross. We were able to map 3 QTLs affecting leaf pubescence based on trichome counts obtained from young leaves (YL) and mature leaves (ML). When the F(2) progeny were classified as pubescent versus glabrous, their ratio did not deviate significantly from a 3:1 model, suggesting that glabrousness is inherited in a simple Mendelian fashion. The glabrous mutation mapped to linkage group A3 at the position of major QTL YL1 and ML1 and appeared orthologous to the t1 locus of the allotetraploids. Interestingly, a fiber mutation, sma-4(ha), observed in the same F(2) population cosegregated with the glabrous marker, which indicates either close linkage or common genetic control of lint fiber and leaf trichomes. Studies of A genome diploids may help to clarify the genetic control of trichomes and fiber in both diploid and tetraploid cottons.

T1 locus in cotton is the candidate gene affecting lint percentage, fiber quality and spiny bollworm (Earias spp.) resistance

A genetic linkage map of chromosome 6 was constructed by using 270 recombinant inbred lines originated from an upland cotton cross (Yumian 1 × T586) F2 population. The genetic map included one morphological (T1) and 18 SSR loci, covering 96.2 cM with an average distance of 5.34 cM between two markers. Based on composite interval mapping (CIM), QTL(s) affecting lint percentage, fiber length, fiber length uniformity, fiber strength and spiny bollworm resistance (Earias spp.) were identified in the t1 locus region on chromosome 6. The allele(s) originating from T586 of QTLs controlling lint percentage increased the trait phenotypic value while the alleles originating from Yumian 1 of QTLs affecting fiber length, fiber length uniformity, fiber strength and spiny bollworm resistance increased the trait phenotypic value.

Putative FLJ20436 gene characterisation in goat : Observed ubiquitous expression in goat and transgenic mice allowed to restrict the location of an hypothesised insulator element

Eukaryotic genomes are organised into independent domains through the establishment of boundaries which allow to have distinct pattern of gene expression both during development and in differentiated cells. The previously reported site independent expression of the mammary-specific goat α-lactalbumin gene in transgenic mice suggested the existence of cis-regulatory elements located upstream of this gene. The nearby presence of a second ubiquitously expressed gene (the cyclin T1 gene) allowed to define two chromatin domains putatively separated by a boundary insulator-like element. In this study, the characterisation of a third putative gene ( FLJ20436) present between the α-lactalbumin and the cyclin T1 loci is reported. It was found to be a functional gene, ubiquitously expressed both in goat and transgenic mice. A complex pattern of alternative splicing events was observed in several analysed tissues leading to various mRNAs and putative FLJ20436 proteins, as suggested in human and mouse species. This allowed us to assign this gene to one of the two hypothesised chromatin domains, refining the location of the potential insulator element.

Substitution of the alpha-lactalbumin transcription unit by a CAT cDNA within a BAC clone silenced the locus in transgenic mice without affecting the physically linked Cyclin T1 gene.

We recently reported that a goat bacterial artificial chromosome (BAC) clone conferred site-independent expression in transgenic mice of the two loci present within its insert, the ubiquitously expressed Cyclin T1 and the mammary specific β-lactalbumin (αlac) genes. To assess if this vector could target mammary-restricted expression of cDNA, the CAT ORF was introduced by homologous recombination in Escherichia coli in place of the αlac transcription unit. The insert of this modified BAC was injected into mice and three transgenic lines were derived. None of these lines expressed the CAT gene suggesting that the use of long genomic inserts is not sufficient to support the expression of intron-less transgenes. The physically linked goat Cyclin T1 locus was found to be active in all three lines. This observation reinforced the hypothesis that the two loci are localised in two separate chromatin domains.

Substitution of the ?-lactalbumin transcription unit by a CAT cDNA within a BAC clone silenced the locus in transgenic mice without affecting the physically linked Cyclin T1 gene

We recently reported that a goat bacterial artificial chromosome (BAC) clone conferred site-independent expression in transgenic mice of the two loci present within its insert, the ubiquitously expressed Cyclin T1 and the mammary specific β-lactalbumin (αlac) genes. To assess if this vector could target mammary-restricted expression of cDNA, the CAT ORF was introduced by homologous recombination in Escherichia coli in place of the αlac transcription unit. The insert of this modified BAC was injected into mice and three transgenic lines were derived. None of these lines expressed the CAT gene suggesting that the use of long genomic inserts is not sufficient to support the expression of intron-less transgenes. The physically linked goat Cyclin T1 locus was found to be active in all three lines. This observation reinforced the hypothesis that the two loci are localised in two separate chromatin domains.

Ubiquitous expression of goat cyclin T1 in transgenic mice.

Ubiquitous gene expression has a variety of applications in transgenesis that include, for example cell lineage analyses in chimeras and gain-of-function related to xenotransplantations. Although several promoters have already been used to these aims, they often do not reliably or reproducibly target gene expression in mice. We have recently reported the site-independent expression of a bacterial artificial chromosome (BAC)-derived goat alpha-lactalbumin transgene in the mammary gland of mice and the subsequent localisation within the insert of this BAC of the cyclin T1 locus. This ubiquitously expressed gene encodes for a protein that acts as a co-factor for the HIV nuclear transcriptional activator. In the present paper, we report that the goat BAC transgene, which encompasses around 30 kb of the cyclin T1 promoter, also confers ubiquitous expression of this gene in the six transgenic mouse lines analysed. These results suggest that the cyclin T1 promoter could be a useful alternative to target ubiquitous gene expression in transgenics.

Distal element(s) is(are) required for position-independent expression of the goat ?-lactalbumin gene in transgenic mice. Potential relationship with the location of the cyclin T1 locus

We recently reported the site-independent and copy-number-related expression in mice of a goat α-lactalbumin gene with 150 kb and 10 kb of 5'- and 3'-flanking sequences, respectively. In the present study, we observed that the resection of the 5'-flanking region, leaving only 70 kb, resulted in a site-dependent expression of this milk protein-encoding transgene. This suggests that important cis-regulatory elements are located within the distal-deleted sequence. Within this region, we localised the promoter of the cyclin T1 gene, an ubiquitously expressed gene. So far, no other gene has been located between these two loci. Since these two genes are differentially expressed, our data suggest the potential location of an insulator within the deleted region that allows the two genes to be independently regulated.

Distal element(s) is(are) required for position-independent expression of the goat alpha-lactalbumin gene in transgenic mice. Potential relationship with the location of the cyclin T1 locus.

We recently reported the site-independent and copy-number-related expression in mice of a goat α-lactalbumin gene with 150 kb and 10 kb of 5'- and 3'-flanking sequences, respectively. In the present study, we observed that the resection of the 5'-flanking region, leaving only 70 kb, resulted in a site-dependent expression of this milk protein-encoding transgene. This suggests that important cis-regulatory elements are located within the distal-deleted sequence. Within this region, we localised the promoter of the cyclin T1 gene, an ubiquitously expressed gene. So far, no other gene has been located between these two loci. Since these two genes are differentially expressed, our data suggest the potential location of an insulator within the deleted region that allows the two genes to be independently regulated.

Molecular mapping of genes affecting pubescence of cotton

Upland cotton (Gossypium hirsutum L.) genotypes have varying densities of trichomes on the leaves and stems of mature plants, hence their species name. Most modern cotton cultivars are ‘‘smooth’’ with few if any trichomes. Absence of trichomes reduces the attractiveness of the cotton plant to some major insect pests, reducing reliance on pesticides. A detailed RFLP map was used to map genes affecting density of leaf and stem trichomes. Based on quantitative measures of young and mature leaves, four QTLs were mapped. A QTL on chromosome 6 that imparts dense leaf pubescence is inferred to be the t1 locus. A second QTL on chromosome 25, which is homoeologous to chromosome 6, fits the description of the t2 locus. Two additional QTLs, QLP1 and QLP2, explained significant phenotypic variation in leaf pubescence—these may represent the t3, t4, or t5 loci. Some QTLs appeared to be specific to particular developmental stages; for example, QLP1 reduced hairiness only in young leaves while QLP2 increased hairiness in mature leaves. A single locus associated with variation in trichome density on the stem did not correspond to the genes/QTLs affecting leaf trichomes, suggesting that these traits may largely be controlled by different genes. A widely used qualitative classification system for scoring trichome density (DTL) detected only the chromosome 6 locus and was apparently not sensitive enough to detect alleles such as t2 that had smaller phenotypic effects.

Genetics and cytology of a new genic male-sterile soybean [ Glycine max (L.) Merr.

Genetic and cytological studies were conducted with a new male-sterile, female-fertile soybean [Glycine max (L.) Merr.] mutant. This mutant was completely male sterile and was inherited as a single-recessive gene. No differences in female or male gamete transmission of the recessive allele were observed between reciprocal cross-pollinations in the F1 or F2 generations. This mutant was not allelic to any previously identified soybean genic male-sterile mutants: ms1, ms2, ms3, ms4, ms5, or ms6. No linkage was detected between sterility and flower color (W1 locus), or between sterility and pubescence color (T1 locus). Light microscopic and cytological observations of microsporogenesis in fertile and sterile anthers were conducted. The structure of microspore mother cells (MMC) in male-sterile plants was identical to the MMCs in male-fertile plants. Enzyme extraction analyses showed that there was no callase activity in male-sterile anthers, and this suggests that sterility was caused by retention of the callose walls, which normally are degraded around tetrads at the late tetrad stage. The tapetum from male-sterile anthers also showed abnormalities at the tetrad stage and later stages, which were expressed by an unusual formation of vacuoles, and by accumulation of densely staining material. At maturity, anthers from sterile plants were devoid of pollen grains.

Quantitative trait loci affecting cotton fiber are linked to the t1 locus in upland cotton

Pilose (T 1), a dominant marker in upland cotton, has been associated with coarse, short fibers. Pilose was, thereby, considered to be pleiotropic on fiber fineness and length. However, a pilose-expressing line with a fiber of average fineness was recently identified. This finding does not support pleiotropy between T 1 and fiber traits, but is indicative of linkage between pilose and loci influencing fiber characteristics. To understand the relationship between T 1 and fiber traits, a pilose line with short, coarse fiber was crossed to two t 1 lines with standard fiber characteristics. One hundred and forty-nine F2-derived F3 lines were developed from one cross, and 60 F2-derived F3 lines from the other. Seven fiber traits (elongation, maturity, micronaire reading, perimeter, 2.5% span length, strength, and wall thickness) were measured. Segregation was normal, as indicated by allelic frequencies of 0.5 for T 1 and t 1, and segregation ratios of 1∶2∶1 for marker genotypes. The association of homozygous T 1 lines with fibers of average fineness was again observed. Linkage between T 1 and loci affecting micronaire, perimeter, 2.5% span length, strength, and wall thickness was found in both populations. Significant additive and non-additive gene effects for each of these traits at the marker locus were found as well. The pilose marker accounted for 10-75% of the phenotypic variation associated with each trait. In conclusion, the t 1 locus is linked to numerous loci that influence fiber traits, and this linkage has previously been misinterpreted as pleiotropy.

New Evidence Relating the Pilose Allele and Micronaire Reading in Cotton

Experiments were undertaken to determine whether close linkage between the pilose allele and a locus influencing cotton (Gossypium hirsutum L.) fiber fineness had been misinterpreted as pleiotropy. Pilose (T1), the dominant allele to the t1 locus, is phenotypically described by a high density of trichomes on the leaf surface, the presence of trichomes on the carpel wall, and increased micronaire. Two lines, 239‐17/6 and 250‐14/2, were derived from single plant selections of pilose plants in an ‘Empire’ genetic background. 239‐17/6 has atypically low micronaire readings. The 239‐17/6 line was crossed to 250‐ 14/2, a pilose, high‐micronaire line, and to lines carrying t1 (normally pubescent) and Tsm1 (glabrous). The F1 plants were selfed for F2 and backcrossefl to t1 and Tsm1 parents. Similar hybrids and backcrosses were made between 250‐14/2 and t1 locus recessives. The agronomic performance and fiber traits of 239‐17/6, 250‐14/2, Empire, and FTA (low micronaire check) were measured for 2 yr in replicated experiments. Lint yield, lint percent, and the fiber traits of elongation, maturity, micronaire, perimeter, span length, strength, and wall thickness were measured. 239‐17/6 expressed a T1 pilose phenotype. All 465 F2 seedlings from 239‐17/6 × 250‐14/2 and reciprocal cross had tomentose leaves. The combined results from crosses of 239‐17/ 6 and 250‐14/2 with t1 and Tsm1, and backcrosses of F1 to t1 and Tsm1 demonstrated that 239‐17/6 and 250‐14/2 both carry T1. The fiber of 239‐17/6 was not distinguishable from the fiber of either Empire or FTA for the wall traits of maturity, micronaire, and wall thickness. 239‐17/6 was shown to have the T1 phenotype and behave genetically like T1. Since T1 was associated with both high and low micronaire readings, the pleiotropic effect of T1 on micronaire appears unlikely. A more likely explanation is the T1 is linked to a gene or block of genes that influence micronaire.