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Abstract Background Manual topping is a routine agronomic practice for balancing the vegetative and reproductive growth of cotton (Gossypium hirsutum) in China, but its cost-effectiveness has decreased over time. Therefore, there is an urgent need to replace manual topping with new approaches, such as biological topping. In this study, we examined the function of GhREV transcription factors (a class III homeodomain-leucine zipper family, HD-ZIP III) in regulating the development of shoot apical meristem (SAM) in cotton with the purpose of providing candidate genes for biological topping of cotton in the future. Results We cloned four orthologous genes of AtREV in cotton, namely GhREV1, GhREV2, GhREV3, and GhREV4. All the GhREVs expressed in roots, stem, leaves, and SAM. Compared with GhREV1 and GhREV3, the expression level of GhREV2 and GhREV4 was higher in the SAM. However, only GhREV2 had transcriptional activity. GhREV2 is localized in the nucleus; and silencing it via virus-induced gene silencing (VIGS) produced an abnormal SAM. Two key genes, GhWUSA10 and GhSTM, which involved in regulating the development of plant SAM, showed about 50% reduction in their transcripts in VIGS-GhREV2 plants. Conclusion GhREV2 positively regulates the development of cotton SAM by regulating GhWUSA10 and GhSTM potentially.

Potassium deficiency causes severe losses in yield and quality in crops. Mepiquat chloride, a plant growth regulator, can increase K+ uptake in cotton (Gossypium hirsutum), but the underlying physiological mechanisms remain unclear. In this study, we used a non-invasive micro-test technique to measure K+ and H+ fluxes in the root apex with or without inhibitors of K+ channels, K+ transporters, non-selective cation channels, and plasma membrane H+-ATPases. We found that soaking seeds in mepiquat chloride solution increased the K+ influx mediated by K+ channels and reduced the K+ efflux mediated by non-selective cation channels in cotton seedlings. Mepiquat chloride also increased negative membrane potential (E m) and the activity of plasma membrane H+-ATPases in roots, due to higher levels of gene expression and protein accumulation of plasma membrane H+-ATPases as well as phosphorylation of H+-ATPase 11 (GhAHA11). Thus, plasma membrane hyperpolarization mediated by H+-ATPases was able to stimulate the activity of K+ channels in roots treated with mepiquat chloride. In addition, reduced K+ efflux under mepiquat chloride treatment was associated with reduced accumulation of H2O2 in roots. Our results provide important insights into the mechanisms of mepiquat chloride-induced K+ uptake in cotton and hence have the potential to help in improving K nutrition for enhancing cotton production. [ABSTRACT FROM AUTHOR]

Mechanical harvesting of cotton is an inevitable trend in China due to the current shortage of farm labor. Row spacings of spindle‐type pickers are adjustable between 76 and 102 cm. However, it is not clear which is better for cotton production in the Yellow River Valley. This field study was conducted under stalk incorporation during 2016–2018, and consisted of experiments of row spacing × nitrogen (N) and row spacing × mepiquat chloride (MC). A split‐plot with four replications was used; row spacings (76, 92 and 102 cm) were assigned as main plots at equal population of 90 000 plants ha−1, and N (0, 105, 210 kg ha−1) or MC rates (0, 140, 281 and 394 g ha−1) as subplots. The wider row spacings (92 and 102 cm) yielded as much as the narrower spacing (76 cm) in 2016 and 2018, but out‐yielded the latter in the wet year (2017) due to the greater number of bolls. Nitrogen application had marginal effects on cotton yield. Mepiquat chloride application increased lint yield by increasing boll weight in 2016–2017, but decreased yield by reducing boll number at the highest rate (394 g ha−1) in the dry year of 2018. Considering plants spaced 92 cm more resistant to lodging than those spaced 102 cm, we suggest the 92 cm spacing may be selected. In addition, the 105–210 kg N ha−1and the 140–281 g MC ha−1 were recommended to balance N removal in seed cotton and get higher or stable yield, respectively. [ABSTRACT FROM AUTHOR]

Potassium (K) deficiency is a key limiting factor in cotton (Gossypium hirsutum) production. By grafting two contrasting cotton cultivars, CCRI41 (more susceptible to K+ deficiency) and SCRC22 (more tolerant of K+ deficiency), we established that cotton shoot plays a vital role in the regulation of root K+ uptake. To identify the genetic basis of this finding, we performed RNA sequencing (RNA-seq) of roots of CCRI41 self-grafts (CCRI41/CCRI41, scion/rootstock) and SCRC22/CCRI41 reciprocal-grafts exposed to K+ deficiency. We found that GhHAK5a, an orthologous of Arabidopsis thaliana high-affinity K+ transporter, AtHAK5, was significantly induced in the CCRI41 rootstock by the SCRC22 scion. This gene was mainly expressed in roots and was more highly induced by K+ deficiency in roots of SCRC22 than those of CCRI41. Agrobacterium-mediated virus-induced gene silencing and yeast complementary assay showed that GhHAK5a is a high-affinity K+ uptake transporter. Importantly, silencing of GhHAK5a in the CCRI41 rootstock almost completely inhibited the K+ uptake induced by SCRC22 scion in CCRI41 rootstock. We identified a key high-affinity K+ transporter, GhHAK5a in cotton, which is the essential target for shoot regulation of root K+ uptake under K+ deficiency. [ABSTRACT FROM AUTHOR]