Stressful environments such as salinity, drought, and high temperature (heat) cause alterations in a wide range of physiological, biochemical, and molecular processes in plants. Photosynthesis, the most fundamental and intricate physiological process in all green plants, is also severely affected in all its phases by such stresses. Since the mechanism of photosynthesis involves various components, including photosynthetic pigments and photosystems, the electron transport system, and CO2 reduction pathways, any damage at any level caused by a stress may reduce the overall photosynthetic capacity of a green plant. Details of the stress-induced damage and adverse effects on different types of pigments, photosystems, components of electron transport system, alterations in the activities of enzymes involved in the mechanism of photosynthesis, and changes in various gas exchange characteristics, particularly of agricultural plants, are considered in this review. In addition, we discussed also progress made during the last two decades in producing transgenic lines of different C3 crops with enhanced photosynthetic performance, which was reached by either the overexpression of C3 enzymes or transcription factors or the incorporation of genes encoding C4 enzymes into C3 plants. We also discussed critically a current, worldwide effort to identify signaling components, such as transcription factors and protein kinases, particularly mitogen-activated protein kinases (MAPKs) involved in stress adaptation in agricultural plants.

Photosynthesis under stressful environments: An overview

Four-way cross (4WC) involving four different inbred lines frequently appears in the cotton breeding programs. However, linkage analysis and quantitative trait loci (QTL) mapping with molecular markers in cotton has largely been applied to populations derived from a cross between two inbred lines, and few results of QTL dissection were conducted in a 4WC population. In this study, an attempt was made to construct a linkage map and identify QTL for yield and fiber quality traits in 4WC derived from four different inbred lines in Gossypium hirsutum L. A linkage map was constructed with 285 SSR loci and one morphological locus, covering 2113.3 cM, approximately 42% of the total recombination length of the cotton genome. A total of 31 QTL with 5.1-25.8% of the total phenotypic variance explained were detected. Twenty-four common QTL across environments showed high stability, and six QTL were environment-specific. Several genomic segments affecting multiple traits were identified. The advantage of QTL mapping using a 4WC were discussed. This study presents the first example of QTL mapping using a 4WC population in upland cotton. The results presented here will enhance the understanding of the genetic basis of yield and fiber quality traits and enable further marker-assisted selection in cultivar populations in upland cotton.

QTL mapping of yield and fiber traits based on a four-way cross population in Gossypium hirsutum L.

Abiotic stress is a major environmental factor that limits cotton growth and yield, moreover, this problem has become more and more serious recently, as multiple stresses often occur simultaneously due to the global climate change and environmental pollution. In this study, we sought to identify genes involved in diverse stresses including abscisic acid (ABA), cold, drought, salinity and alkalinity by comparative microarray analysis. Our result showed that 5790, 3067, 5608, 778 and 6148 transcripts, were differentially expressed in cotton seedlings under treatment of ABA (1μM ABA), cold (4°C), drought (200mM mannitol), salinity (200mM NaCl) and alkalinity (pH=11) respectively. Among the induced or suppressed genes, 126 transcripts were shared by all of the five kinds of abiotic stresses, with 64 up-regulated and 62 down-regulated. These common members are grouped as stress signal transduction, transcription factors (TFs), stress response/defense proteins, metabolism, transport facilitation, as well as cell wall/structure, according to the function annotation. We also noticed that large proportion of significant differentially expressed genes specifically regulated in response to different stress. Nine of the common transcripts of multiple stresses were selected for further validation with quantitative real time RT-PCR (qRT-PCR). Furthermore, several well characterized TF families, for example, WRKY, MYB, NAC, AP2/ERF and zinc finger were shown to be involved in different stresses. As an original report using comparative microarray to analyze transcriptome of cotton under five abiotic stresses, valuable information about functional genes and related pathways of anti-stress, and/or stress tolerance in cotton seedlings was unveiled in our result. Besides this, some important common factors were focused for detailed identification and characterization. According to our analysis, it suggested that there was crosstalk of responsive genes or pathways to multiple abiotic or even biotic stresses, in cotton. These candidate genes will be worthy of functional study under diverse stresses.

/pdf/transcriptome-analysis-reveals-crosstalk-of-responsive-genes-18j8c8ql2r.pdf

Transcriptome analysis reveals crosstalk of responsive genes to multiple abiotic stresses in cotton (Gossypium hirsutum L.).

Seeking a simple and moderate route to generate reactive oxygen species (ROS) for antibiosis is of great interest and challenge. This work demonstrates that molecule transition and electron rearrangement processes can directly occur only through chemisorption interaction between the adsorbed O2 and high-energy {111} facet-exposed MgO with abundant surface oxygen vacancies (SOVs), hence producing singlet oxygen and superoxide anion radicals without light irradiation. These ROS were confirmed by electron paramagnetic resonance, in situ Raman, and scavenger experiments. Furthermore, heat plays a crucial role for the electron transfer process to accelerate the formation of ·O2–, which is verified by temperature kinetic experiments of nitro blue tetrazolium reduction in the dark. Therefore, the presence of oxygen vacancy can be considered as an intensification of the activation process. The designed MgO is acquired in one step via constructing a reduction atmosphere during the combustion reaction process, whic...

Synthesis of {111} Facet-Exposed MgO with Surface Oxygen Vacancies for Reactive Oxygen Species Generation in the Dark

The superior fiber properties of Gossypium barbadense L. serve as a source of novel variation for improving fiber quality in Upland cotton (G. hirsutum L.), but introgression from G. barbadense has been largely unsuccessful due to hybrid breakdown and a lack of genetic and genomic resources. In an effort to overcome these limitations, we constructed a linkage map and conducted a quantitative trait locus (QTL) analysis of 10 agronomic and fiber quality traits in a recombinant inbred mapping population derived from a cross between TM-1, an Upland cotton line, and NM24016, an elite G. hirsutum line with stabilized introgression from G. barbadense. The linkage map consisted of 429 simple-sequence repeat (SSR) and 412 genotyping-by-sequencing (GBS)-based single-nucleotide polymorphism (SNP) marker loci that covered half of the tetraploid cotton genome. Notably, the 841 marker loci were unevenly distributed among the 26 chromosomes of tetraploid cotton. The 10 traits evaluated on the TM-1 × NM24016 population in a multienvironment trial were highly heritable, and most of the fiber traits showed considerable transgressive variation. Through the QTL analysis, we identified a total of 28 QTLs associated with the 10 traits. Our study provides a novel resource that can be used by breeders and geneticists for the genetic improvement of agronomic and fiber quality traits in Upland cotton. A s the world’s foremost natural fiber crop, cotton supports a multibillion-dollar production and pro

Linkage Map Construction and Quantitative Trait Locus Analysis of Agronomic and Fiber Quality Traits in Cotton

Haploid seed-producing semigamy in cotton is controlled by a single incompletely dominant gene (Se). However, its molecular mechanism is currently poorly understood. In this study, the mRNA differential display (DD) was employed to compare gene expression between non-semigametic Pima S-1 (Gossypium barbadense) and its naturally occurring semigametic mutant 57–4. Of the 70 DD cDNA fragments isolated from a total of 3,000 cDNA fragments, some exhibited semigamy-specific expression across anthers and/or ovules. Of the 61 cDNA fragments cloned and sequenced, nine showed high homology to genes encoding for α-tubulin, SPK1, Rab11, sucrose synthase, isocitrate lyase, phosphoethanolamine N-methyltransferase, phospholipase D, MADS 7, and WRKY 2. From cDNA–single-strand conformational polymorphism using primers designed from DD sequences, qualitative expression differences in six genes between the semigametic and non-semigametic genotypes were validated. However, a primer pair designed from an α-tubulin gene sequence yielded PCR products with quantitative difference in band intensity, which is linked to the semigamy gene at a recombination frequency of 0.316 in a (57–4 × Pima S-1) × Pima S-1 BC1F1 population. Its expression in the semigametic 57–4 anthers was suppressed by 2-fold as compared to that in Pima S-1 using a quantitative reverse transcription PCR analysis. This study identified several novel genes that were missed in prior microarray analysis, and their potential roles with regards to reproductive biology are discussed.

Identification of Differentially Expressed Genes in Semigametic Pima Cotton by Differential Display

Semigamy, controlled by one incomplete dominant gene (Se) in Pima cotton (Gossypium barbadense), is an aberrant form of sexual reproduction or apomixis, in which the sperm and egg nuclei fail to fuse and proceed to develop independently resulting in various outcomes, such as haploids, diploids, and chimeras. The objective of this study was to develop molecular markers linked to the semigamy gene using a (Pima S-1 × 57-4) × Pima S-1 BC1F1 mapping population consisting of 34 semigametic and 30 non-semigametic progenies. Random amplified polymorphic DNA (RAPD), amplified fragment length polymorphism (AFLP), ATG-anchored AFLP (ATG-AFLP), sequenced tagged site (STS), and single-strand conformational polymorphism (SSCP) markers were tested. None of the apparent polymorphic RAPD, AFLP, and ATG-AFLP markers were linked to the semigamy gene, while three polymorphic markers developed from genes based on comparative microarray and differential display analyses, SSCP Se18-1800 and Se18-3000, and STS Se19, were mapped to a linkage group carrying the semigamy gene. The results present evidence that targeted gene mapping is an efficient method using markers developed from comparative gene expression studies. The current work represents the first study in identifying DNA markers associated with semigamy in plants, providing an incentive toward high-resolution mapping and isolation of the semigamy gene.

Jessica Curtiss

Papers

Identification of Differentially Expressed Genes in Semigametic Pima Cotton by Differential Display

Identification of Molecular Markers Associated with Semigamy in Cotton