Li Zhaohu

Conditions and Indicators for Screening Cotton (Gossypium hirsutum L.) Varieties Tolerant to Low Potassium

Abstract To establish a screening system for evaluating the tolerance of cotton ( Gossypium hirsutum L.) varieties to low potassium (K), 50 cotton varieties that covered more than 80% planting area in China in 2004 were used in a hydroponic sculture and a field experiment in 2006. The K concentrations were 0.02 (low K stress) and 2.50 mmol L −1 (high K), respectively, in the hydroponic culture, and the available K in soil was 59.88 mg kg −1 (K deficient). At 5-leaf stage, the total plant dry weight (DW) varied larger among cotton varieties than that at 3-leaf stage; thus, seedlings at 5-leaf stage were adapted in the comparison of tolerance to low K. Under the low K condition, DW was significantly correlated with the relative dry weight (RDW) ( r = 0.7690, P r = 0.9522, P r = 0.9791, P r = 0.5201, P r = 0.3325, P r = −0.4455, P r = 0.5091, P

Effects of Potassium Deficiency on Root Growth of Cotton Seedlings and Its Physiological Mechanisms

Abstract For the purpose of dissecting the mechanism of root growth in response to potassium (K) deficiency in cotton (Gossypium hirsutum L.), young seedlings of NuCOTN99B grown in half-strength modified Hoaglands solution with low K nutrient (0.05 mmol L−1) were investigated for the root configuration, content of endogenous free indole acetic acid (IAA), and amount of ethylene released from the roots 4 d after treatment. Compared with the treatment with moderate K nutrient (0.50 mmol L−1, control), the K deficient treatment significantly inhibited root length and the formation of lateral roots. The reduced lateral roots mainly resulted from the shortened branched root zone, and there was no change in the lateral root density. Under K deficient condition, the greatest reductions for root length, total root surface area, and root volume occurred in fine roots (0.05 mm ≤ diameter

Transgenic cotton could safely be grown since CpTI toxin rapidly degrades in the rhizosphere soil

Abstract Cultivation of transgenic plants is debated worldwide. Potential environmental risks have to be considered, before acceptance of expanding cultivation, despite the advantages of the use of fewer pesticides. Here, the potential effects on soil ecosystems of transgenic plants have been studied. As a model, genetically engineered cotton producing cowpea trypsin inhibitor (CpTI) has been used. The degradation of CpTI in the rhizosphere of the transgenic CpTI+Bt (Bacillus thuringiensis) cotton cultivar SGK321 was assessed. During plant development, concentrations of CpTI toxin in the rhizosphere were measured using an enzyme-linked immunosorbent assay (ELISA). As the plants developed, the residue of CpTI in the rhizosphere increased, and reached a peak at topping stage (100 days after planting). After this stage, the residue began to decrease, and was nil the following year (258 days after planting). The conclusion is that genetically engineered cotton can safely be cultivated since no accumulation of substances released from the transgenic plants was persistent in the soil.

NaCl-Induced Changes of Ion Fluxes in Roots of Transgenic Bacillus thuringiensis (Bt) Cotton (Gossypium hirsutum L.)

Abstract Bacillus thuringiensis (Bt) cotton is grown worldwide, including in saline soils, but the effect of salinity on ion fluxes of Bt cotton remains unknown. Responses of two transgenic Bt cotton genotypes (SGK321 and 29317) and their corresponding receptors, Shiyuan 321 (SY321) and Jihe 321 (J321), to 150 mmol L −1 NaCl stress were studied in a growth chamber. The root dry weight of SGK321 and 29317 under NaCl treatment was decreased by 30 and 31%, respectively. However, their corresponding receptor cultivars SY321 and J321 were less affected (19 and 24%, respectively). The root length and surface area of the Bt cultivars were significantly decreased relative to their receptors under salt stress. NaCl treatment significantly increased Cry1Ac mRNA transcript levels in SGK321 and 29317 but did not affect Bt protein content in leaves or roots of either cultivar at 1 and 7 d after NaCl treatment. Fluxes of Na + , K + , and H + in roots were investigated using the scanning ion-selective electrode technique. Both mean K+ efflux rate and transient K + efflux of the Bt cultivars increased four-fold compared to their corresponding receptors when exposed to salinity stress. There were no significant differences in Na + efflux between Bt and non-Bt cottons. Furthermore, the Na + contents in roots and leaves of all genotypes dramatically increased under salt stress, whereas K + contents decreased. Our results suggested that Bt cotton cultivars are more sensitive to salt stress than their receptor genotypes.

Evaluation of Harvest Aid Chemicals for the Cotton-Winter Wheat Double Cropping System

Abstract Timing of harvest is critical for mechanical picking in cotton production, especially in those regions with double cropping system. Appropriate and safe harvest aids will improve timing and facilitate harvest of cotton in the double cropping system. Three defoliants (dimethipin, thidiazuron, and thidiazuron-diuron) and one boll opener (ethephon) were included in this research. They were evaluated for their effects on defoliation, boll opening, seedcotton yield, seed quality, and fiber quality of field grown cotton when used alone or as a mixture in 2009 and 2010. Defoliation and/or boll opening were increased by all three defoliants and ethephon, especially by mixtures of a defoliant and ethephon. First harvest of seedcotton was significantly increased with defoliant-ethephon mixtures. No significant adverse effects were observed on boll weight, lint percentage, seed quality, and fiber properties. It was estimated that tank mixes of ethephon and one of the three defoliants can improve the adjusted gross revenue. Boll opening can be used as an alternative indicator for the adjusted gross revenue, because, it was linearly and positively correlated with the relative adjusted gross revenue and convenient in measurements. Wheat seedling growth was not affected by thidiazuron, whereas its seedling emergence, root dry weight, relative water content, and electrolyte leakage were adversely affected by dimethipin and thidiazuron-diuron when concentration was above 340 and 100 g (a.i.) ha−1, respectively. 90% defoliation and 80% boll opening were observed with the high rate of thidiazuron-ethephon mixture, but no adverse effects on winter wheat. The results suggested that tank mixes of ethephon with thidiazuron can be used effectively and safely in the cotton-winter wheat double cropping system to improve yield without adverse effects on seed quality and fiber quality.

Mechanism of Tolerance to Potassium Deficiency Between Liaomian 18 and NuCOTN99B at Seedling Stage

Abstract The objective of the present study was to elucidate the mechanism of tolerance to potassium (K) deficiency in cotton ( Gossypium hirsutum L.) through comparing the differences of K uptake, translocation, and utilization in a K-efficient cultivar Liaomian 18 (non-Bt cotton) and a K-inefficient cultivar NuCOTN99B (American Bt cotton). The seedlings of the 2 cultivars were hydroponically cultured in a growth chamber and treated with sufficient K of 2.5 mmol L −1 (control) or deficient K of 0.03 mmol L −1 . There was no significant difference in dry matter yield of seedlings between both cultivars under the control condition, whereas Liaomian 18 produced 170% more dry matter than NuCOTN99B in the K-deficient solution. Under the K-deficient condition, the amounts of K uptake per unit root dry weight, per unit root length, and per unit root surface area in Liaomian 18 were similar to or lower than those in NuCOTN99B, and the ratio of K accumulation in leaf to that in whole plant was 57.7% and 67.6% in Liaomian 18 and NuCOTN99B, respectively. These results indicated that the higher K-efficiency of Liaomian 18, compared with NuCOTN99B, was independent of its capacities for root physiological uptake and translocation of K to leaf. In contrast, Liaomian 18 had larger root system than NuCOTN99B, and its root length, root surface area, and root volume were 3.4, 3.8, and 4.2 folds higher than those of NuCOTN99B, respectively. In addition, the K utilization index (dry matter produced per unit of K concentration) in Liaomian 18 was 147% higher than that in NuCOTN99B. Therefore, the higher tolerance to K deficiency in Liaomian 18 possibly depended on its larger root system and greater internal K utilization efficiency. On account of the insignificant differences in osmotic potential and relative water content in leaf between Liaomian 18 and NuCOTN99B, the higher internal K utilization efficiency of Liaomian 18 was deduced to be associated with the biochemical function of K rather than the biophysical function of K.

Expression characteristics of GFP driven by NAC1 promoter and its responses to auxin and gibberellin

Abstract Abstract A 1050 bp fragment upstream transcription start site of a transcription factor gene NAC1 in Arabidopsis thaliana was amplified and cloned into plasmid pRD420 to construct a green fluorescent protein (GFP) fusion system under the control of NAC1 promoter. Plasmids were introduced into tobacco by Agrobacterium-mediated method to regenerate plants with NAC1-GFP gene, and expression pattern of NAC1-GFP and is responses to auxin and gibberellin (GA) were observed. GFP was found to accumulate specifically in root, and was detected after treatment of auxin, N-1-Naphthylphthalamic acid (NPA, an auxin antagonist) or GA3. It was indicated that the expression of GFP driven by NAC1 promoter was induced not only by auxin but also by Gas, suggesting that NAC1 mediated both the auxin signaling and the Gas signaling involved in lateral roots development. * Supported by National Natural Science Foundation of China (Grant No. 30200169) and Specialized Research Fund for the Doctoral Program of Higher Educa...

Analysis of differential expression of genes induced by ethephon in elongating internodes of maize plants

Plant growth regulators (PGRs) are commonly used in cereal cropping systems to restrict plant height and control lodging. Ethephon has been reported to shorten internodes and increase grain yield of maize. To analyze the transcriptomic profiles of maize internode elongation following ethephon treatment, differentially expressed genes were compared between the treatment and control samples of inbred line Zong 31 using the Affymetrix Maize Genome Array. According to the microarray data, 326 probe sets showed significant change in expression. Further research revealed that the most remarkable effects of ethephon on maize internodes elongation occurred during a 48 h period, when 89 differentially expressed genes were detected. There were dramatic change in transcript levels at 24 h and six Auxin transport genes and four gibberellin biosynthesis pathway genes were differ- entially expressed in Zong 31 in response to ethephon treatment. In summary, we showed that gaseous ethylene release is involved in internode meristem cell elongation through the regulation of plant hormone signaling in maize. This work provides a platform for studies in which candidate genes will be functionally tested for involve- ment in internode elongation.

Study on the Mitochondrial Genome of Sea Island Cotton (Gossypium barbadense) by BAC Library Screening

The plant mitochondrial genome displays complex features, particularly in terms of cytoplasmic male sterility (CMS). Therefore, research on the cotton mitochondrial genome may provide important information for analyzing genome evolution and exploring the molecular mechanism of CMS. In this paper, we present a preliminary study on the mitochondrial genome of sea island cotton (Gossypium barbadense) based on positive clones from the bacterial artificial chromosome (BAC) library. Thirty-five primers designed with the conserved sequences of functional genes and exons of mitochondria were used to screen positive clones in the genome library of the sea island cotton variety called Pima 90-53. Ten BAC clones were obtained and verified for further study. A contig was obtained based on six overlapping clones and subsequently laid out primarily on the mitochondrial genome. One BAC clone, clone 6 harbored with the inserter of approximate 115 kb mtDNA sequence, in which more than 10 primers fragments could be amplified, was sequenced and assembled using the Solexa strategy. Fifteen mitochondrial functional genes were revealed in clone 6 by gene annotation. The characteristics of the syntenic gene/exon of the sequences and RNA editing were preliminarily predicted.

Effect of Brassinolide on Leaf Photosynthetic Function and Yield in Spring Maize Filling Stage

A field experiment was conducted to investigate the effect of plant growth regulator brassinolide(BR) on the regulation of physiological activities of ear leaf, the grain filling and yield in spring maize(Zea mays L., cv. Zhengdan 958). Husks and ear leaves were treated with BR at 15 days after anthesis by foliar spraying. The results showed that the chlorophyll content, photosynthetic rate and activities of PEP carboxylaes, Ru BP carboxylase, sucrose synthase and sucrose phosphate synthase in ear leaf as well as source content in kernel were significantly reduced, while starch accumulation and dry weight of kernel were increased during grain filling. BR significantly increased the content of chlorophyll and photosynthetic rate, enhanced the activities of PEP carboxylaes and Ru BP carboxylase, definitely resulting in enhanced CO2 assimilation. BR markedly increased the activities of sucrose synthase and sucrose phosphate synthase in ear leaf. And in kernel, the accumulation of sucrose and starch as well as the grain filling rate were accelerated by BR. BR treatment significantly reduced the length of ear barren tip, and increased the number of kernels per ear, which led to higher yield. These results suggest that BR treatment at filling stage may be a good strategy to get a high yield in maize, by enhancing activity of resource, delaying sencence and stimulating the flow of assimilate from the source to the sink.