Background: Nucleobase–ascorbate transporters(NAT), synonymously called nucleobase–cation symporter 2(NCS2) proteins, were earlier reported to be involved in plant growth, development and resistance to stress. Previous studies concluded that s a polymorphic SNP associated with NAT12 was significant di erent between salt-tolerant and salt-sensitive materials of upland cotton. In current study, a comprehensive analysis of NAT family genes was conducted for the first time in cotton.Results: In this study, we discovered 32, 32, 18, and 16 NAT genes in Gossypium hirsutum, G. barbadense, G. raimondii and G. arboreum, respectively, which were classified into four groups(groups I–IV) based on the multiple sequence analysis. These GhNAT genes were unevenly distributed on At and Dt sub-genome in G. hirsutum. Most GhNAT members in the same group had similar gene structure characteristics and motif composition. The collinearity analysis revealed segmental duplication as well as tandem duplication contributing to the expansion of the GhNATs. The analysis of cis-acting regulatory elements of GhNATs showed that the function of GhNAT genes in cotton might be related to plant hormone and stress response. Under di erent conditions, the expression levels further suggested the GhNAT family genes were associated with plant response to various abiotic stresses. GhNAT12 was detected in the plasma membrane. And it was validated that the GhNAT12 gene played an important role in regulating cotton resistance to salt and drought stress through the virus-induced gene silencing(VIGS) analysis.Conclusions: A comprehensive analysis of NAT gene family was performed in cotton, including phylogenetic analysis, chromosomal location, collinearity analysis, motifs, gene structure and so on. Our results will further broaden the insight into the evolution and potential functions of NAT genes in cotton. Current findings could make significant contribution towards screening more candidate genes related to biotic and abiotic resistance for the improvement in cotton.

Background: Gossypium hirsutum(upland cotton) is one of the principal fiber crops in the world. Cotton yield is highly affected by abiotic stresses, among which salt stress is considered as a major problem around the globe. Transgenic approach is efficient to improve cotton salt tolerance but depending on the availability of salt tolerance genes.Results: In this study we evaluated salt tolerance candidate gene ST7 from Thellungiella halophila, encoding a homolog of Arabidopsis aluminum-induced protein, in cotton. Our results showed that ThST7 overexpression in cotton improved germination under NaCl stress as well as seedling growth. Our field trials also showed that ThST7 transgenic cotton lines produced higher yield under salt stress conditions. The improved salt tolerance of the transgenic cotton lines was partially contributed by enhanced antioxidation as shown by diaminobenzidine(DAB) and nitrotetrazolium blue chloride(NBT) staining. Moreover, transcriptomic analysis of ThST7 overexpression lines showed a significant upregulation of the genes involved in ion homeostasis and antioxidation, consistent with the salt tolerance phenotype of the transgenic cotton.Conclusions: Our results demonstrate that ThST7 has the ability to improve salt tolerance in cotton. The ThST7 transgenic cotton may be used in cotton breeding for salt tolerance cultivars.

Australian cotton production predominantly occurs on Vertisols. The average lint yield of cotton grown in Australia is 2 260–2 700 kg·hm~(-2), which is 2.5 to 3 times the world average. This high productivity per unit of land area requires e cient use of resources such as water and nutrients. However, high yields accelerate the export of nutrients such as phosphorus(P) in seed, depleting the soil reserves of P more than in other countries with lower cotton yields. Recent surveys of cotton industry indicate that P application rates should match seed P export(30～ 40 kg·hm~(-2)), but historical depletion within subsoil is still evident and is continuing. Depletion of soil P is typically more pronounced in the subsoil than in the topsoil(0～ 20 cm) where P fertiliser is applied, as cotton roots rely on these layers as important sources of plant available water and available P. This mismatch between zones of P uptake and resupply may increase stratification of available P in the soil profile. Recent studies showed that cotton responded poorly to banded applications of fertiliser P, while dispersal of fertiliser throughout the plant beds was more successful. Researchers have also observed sporadic cotton responses to applied P fertiliser in soils where available P concentrations were well above the previously determined critical concentrations indicative of fertiliser P responses in Australia. To sustain highyielding cotton production in Australia, a greater understanding of cotton root acquisition of applied P, as well as a re-examination of critical soil P concentrations for each production region are required.

Trifloxysulfuron(Envoke) is an acetolactate synthase-inhibitor herbicide and can be used to control many broadleaf weeds and nutsedges in cotton production.However,there is a lack of information on genotypic variation in response to the herbicide.In this field study,60 Pima(Gossypium barbadense L.) lines,122 Upland(G.hirsutum L.) lines,and 9 Upland x Pima segregating populations were divided into five tests(18 A,18 B,18 G,18 RB,and 18 HQ) to evaluate trifloxysulfuron tolerance at the 7-true leaf stage(42 days after planting) under the same field conditions in 201 8.Across the five tests,Pima cotton genotypes tested in this study did not show any visual crop injury based on percentage of plants with chlorosis at 6 days after treatment(DAT),indicating consistent and high levels of trifloxysulfuron tolerance.However,the response to trifloxysulfuron within U pland cotton is highly variable.While U pland cotton is overall more sensitive to trifloxysulfuron with crop injury up to 80% than Pima cotton,1 9 lines had injury below 5% including one line with no visual injury,and 19 lines had injury between 5% and 10%.In test 18 HQ with 15 transgenic Upland cultivars and 17 non-transgenic Upland lines,the analysis of variance detected a significant genotypic difference.The broad-sense heritability estimates for trifloxysulfuron tolerance based on crop injury at 6 DAT was 0.555,suggesting that trifloxysulfuron tolerance in U pland cotton is moderately heritable.This study represents the first report that Pima cotton and many Upland cotton lines are highly tolerant to trifloxysulfuron with no or little crop injury.