Jingjuan Zhang

Bio: Jingjuan Zhang is an academic researcher from Murdoch University. The author has contributed to research in topics: Gene & Quantitative trait locus. The author has an hindex of 12, co-authored 37 publications receiving 581 citations.

GA-20 oxidase as a candidate for the semidwarf gene sdw1/denso in barley

Abstract: The barley sdw1/denso gene not only controls plant height but also yield and quality. The sdw1/denso gene was mapped to the long arm of chromosome 3H. Comparative genomic analysis revealed that the sdw1/denso gene was located in the syntenic region of the rice semidwarf gene sd1 on chromosome 1. The sd1 gene encodes a gibberellic acid (GA)-20 oxidase enzyme. The gene ortholog of rice sd1 was isolated from barley using polymerase chain reaction. The barley and rice genes showed a similar gene structure consisting of three exons and two introns. Both genes share 88.3% genomic sequence similarity and 89% amino acid sequence identity. A single nucleotide polymorphism was identified in intron 2 between barley varieties Baudin and AC Metcalfe with Baudin known to contain the denso semidwarf gene. The single nucleotide polymorphism (SNP) marker was mapped to chromosome 3H in a doubled haploid population of Baudin × AC Metcalfe with 178 DH lines. Quantitative trait locus analysis revealed that plant height cosegregated with the SNP. The sdw1/denso gene in barley is the most likely ortholog of the sd1 in rice. The result will facilitate understanding of the molecular mechanism controlling semidwarf phenotype and provide a diagnostic marker for selection of semidwarf gene in barley.

Water deficits in wheat: fructan exohydrolase (1-FEH) mRNA expression and relationship to soluble carbohydrate concentrations in two varieties

Abstract: Terminal drought is a risk for wheat production in many parts of the world. Robust physiological traits for resilience would enhance the preselection of breeding lines in drought-prone areas. • Three pot experiments were undertaken to characterize stem water-soluble carbohydrate (WSC), fructan exohydrolase expression, grain filling and leaf gas exchange in wheat (Triticum aestivum) varieties, Kauz and Westonia, which are considered to be drought-tolerant. • Water deficit accelerated the remobilization of stem WSC in Westonia but not in Kauz. The profile of WSC accumulation and loss was negatively correlated with the mRNA concentration of 1-FEH, especially 1-FEH w3 (1-FEH-6B). Under water deficit, Westonia showed lower concentrations of WSC than Kauz but did not show a corresponding drop in grain yield. • The results from pot experiments suggest that stem WSC concentration is not, on its own, a reliable criterion to identify potential grain yield in wheat exposed to water deficits during grain filling. The expression of 1-FEH w3 may provide a better indicator when linked to osmotic potential and green leaf retention, and this requires validation in field-grown plants.

A wheat 1‐FEH w3 variant underlies enzyme activity for stem WSC remobilization to grain under drought

Abstract: In wheat stems, the levels of fructan-dominated water-soluble carbohydrates (WSC) do not always correlate well with grain yield. Field drought experiments were carried out to further explain this lack of correlation. Wheat (Triticum aestivum) varieties, Westonia, Kauz and c. 20 genetically diverse double haploid (DH) lines derived from them were investigated. Substantial genotypic differences in fructan remobilization were found and the 1-FEH w3 gene was shown to be the major contributor in the stem fructan remobilization process based on enzyme activity and gene expression results. A single nucleotide polymorphism (SNP) was detected in an auxin response element in the 1-FEH w3 promoter region, therefore we speculated that the mutated Westonia allele might affect gene expression and enzyme activity levels. A cleaved amplified polymorphic (CAP) marker was generated from the SNP. The harvested results showed that the mutated Westonia 1-FEH w3 allele was associated with a higher thousand grain weight (TGW) under drought conditions in 2011 and 2012. These results indicated that higher gene expression of 1-FEH w3 and 1-FEH w3 mediated enzyme activities that favoured stem WSC remobilization to the grains. The CAP marker residing in the 1-FEH w3 promoter region may facilitate wheat breeding by selecting lines with high stem fructan remobilization capacity under terminal drought.

Wild-type alleles of Rht-B1 and Rht-D1 as independent determinants of thousand-grain weight and kernel number per spike in wheat

Abstract: The utilization of dwarfing genes Rht-B1b and Rht-D1b in wheat significantly increased grain yield and contributed to the ''green revolution''. However, the benefit of Rht-B1b and Rht-D1b in drought environments has been debated. Although quantitative trait loci (QTL) for kernel number per spike (KN) and thousand-grain weight (TGW) have been found to be associated with Rht-B1 and Rht-D1, the confounding effect of environmental variation has made a direct association difficult to find. In this study, we used a doubled haploid population (225 lines) of Westonia 9 Kauz, in which both Rht-B1b (Kauz) and Rht-D1b (Westonia) segregated. The purpose of the study was to determine the interaction of Rht-B1 and Rht-D1 with grain yield components, namely KN and TGW, and to investigate genotype-by-environment interactions in glasshouse and field trials conducted in 2010 and 2011 in Western Australia. A genetic map of 1,156 loci was constructed using 195 microsatellite markers, two gene-based markers for Rht-B1 and Rht- D1, and 959 single nucleotide polymorphisms. The major QTL for TGW and KN were strongly linked to Rht-B1 and Rht-D1 loci and the positive effects were associated with the wild-type alleles, Rht-B1a and Rht- D1a. The major QTL of TGW were on chromosome 2D and 4B. The significant genetic effects (14.6-22.9 %) of TGW indicated that marker-assisted selection for TGW is possible, and markers gwm192a (206 bp) or gwm192b (236 bp) can be used as indicators of high TGW. For KN, one major QTL was detected on chromosome 4D in the analysis across three environments. The association of the wild-type alleles Rht-B1a and Rht-D1a in drought environments is discussed.

Impact of mid-season sulphur deficiency on wheat nitrogen metabolism and biosynthesis of grain protein.

Abstract: Wheat (Triticum aestivum) quality is mainly determined by grain storage protein compositions. Sulphur availability is essential for the biosynthesis of the main wheat storage proteins. In this study, the impact of different sulphur fertilizer regimes on a range of agronomically important traits and associated gene networks was studied. High-performance liquid chromatography was used to analyse the protein compositions of grains grown under four different sulphur treatments. Results revealed that sulphur supplementation had a significant effect on grain yield, harvest index, and storage protein compositions. Consequently, two comparative sulphur fertilizer treatments (0 and 30 kg ha-1 sulphur, with 50 kg ha-1 nitrogen) at seven days post-anthesis were selected for a transcriptomics analysis to screen for differentially expressed genes (DEGs) involved in the regulation of sulphur metabolic pathways. The International Wheat Genome Sequencing Consortium chromosome survey sequence was used as reference. Higher sulphur supply led to one up-regulated DEG and sixty-three down-regulated DEGs. Gene ontology enrichment showed that four down-regulated DEGs were significantly enriched in nitrogen metabolic pathway related annotation, three of which were annotated as glutamine synthetase. The Kyoto Encyclopedia of Genes and Genomes pathway enrichment identified three significantly enriched pathways involved in nitrogen and amino acid metabolism.

Integrated genomics, physiology and breeding approaches for improving drought tolerance in crops.

Abstract: Drought is one of the most serious production constraint for world agriculture and is projected to worsen with anticipated climate change. Inter-disciplinary scientists have been trying to understand and dissect the mechanisms of plant tolerance to drought stress using a variety of approaches; however, success has been limited. Modern genomics and genetic approaches coupled with advances in precise phenotyping and breeding methodologies are expected to more effectively unravel the genes and metabolic pathways that confer drought tolerance in crops. This article discusses the most recent advances in plant physiology for precision phenotyping of drought response, a vital step before implementing the genetic and molecular-physiological strategies to unravel the complex multilayered drought tolerance mechanism and further exploration using molecular breeding approaches for crop improvement. Emphasis has been given to molecular dissection of drought tolerance by QTL or gene discovery through linkage and association mapping, QTL cloning, candidate gene identification, transcriptomics and functional genomics. Molecular breeding approaches such as marker-assisted backcrossing, marker-assisted recurrent selection and genome-wide selection have been suggested to be integrated in crop improvement strategies to develop drought-tolerant cultivars that will enhance food security in the context of a changing and more variable climate.

The Role of Drought in Outbreaks of Plant-eating Insects

Abstract: Substantial evidence indicates that drought stress promotes outbreaks of plant-eating (phytophagous) fungi and insects. Observations and experiments show that colonization success and pervalence of such fungi as root and stalk rots, stem cankers, and sometimes wilts and foliar diseases are much higher on water-stressed plants than on normal plants (Schoeneweiss 1986). The evidence associating insects and drought is more circumstantial, consisting largely of observations that outbreaks around the world of such insects as bark beetles and leaf feeders (see Table 1) are typically preceded by unusually warm, dry weather. There is also a consistent, positive correlation between insect oubreaks and dry, nutrient-poor sites (Mattson and Haack 1987).

Development and validation of KASP assays for genes underpinning key economic traits in bread wheat.

Abstract: We developed and validated a robust marker toolkit for high-throughput and cost-effective screening of a large number of functional genes in wheat. Functional markers (FMs) are the most valuable markers for crop breeding programs, and high-throughput genotyping for FMs could provide an excellent opportunity to effectively practice marker-assisted selection while breeding cultivars. Here we developed and validated kompetitive allele-specific PCR (KASP) assays for genes that underpin economically important traits in bread wheat including adaptability, grain yield, quality, and biotic and abiotic stress resistances. In total, 70 KASP assays either developed in this study or obtained from public databases were validated for reliability in application. The validation of KASP assays were conducted by (a) comparing the assays with available gel-based PCR markers on 23 diverse wheat accessions, (b) validation of the derived allelic information using phenotypes of a panel comprised of 300 diverse cultivars from China and 13 other countries, and (c) additional testing, where possible, of the assays in four segregating populations. All KASP assays being reported were significantly associated with the relevant phenotypes in the cultivars panel and bi-parental populations, thus revealing potential application in wheat breeding programs. The results revealed 45 times superiority of the KASP assays in speed than gel-based PCR markers. KASP has recently emerged as single-plex high-throughput genotyping technology; this is the first report on high-throughput screening of a large number of functional genes in a major crop. Such assays could greatly accelerate the characterization of crossing parents and advanced lines for marker-assisted selection and can complement the inflexible, high-density SNP arrays. Our results offer a robust and reliable molecular marker toolkit that can contribute towards maximizing genetic gains in wheat breeding programs.

Multifunctional fructans and raffinose family oligosaccharides.

Abstract: Fructans and Raffinose Family Oligosaccharides (RFOs) are the two most important classes of water soluble carbohydrates in plants. Recent progress is summarized on their metabolism (and regulation) and on their functions in plants and in food (prebiotics, antioxidants). Interest has shifted from the classic inulin-type fructans to more complex fructans. Similarly, alternative RFOs were discovered next to the classic RFOs. Considerable progress has been made in the understanding of structure-function relationships among different kinds of plant fructan metabolizing enzymes. This helps to understand their evolution from (invertase) ancestors, and the evolution and role of so-called “defective invertases”. Both fructans and RFOs can act as reserve carbohydrates, membrane stabilizers and stress tolerance mediators. Fructan metabolism can also play a role in osmoregulation (e.g. flower opening) and source-sink relationships. Here, two novel emerging roles are highlighted. First, fructans and RFOs may contribute to overall cellular ROS homeostasis by specific ROS scavenging processes in the vicinity of organellar membranes (e.g. vacuole, chloroplasts). Second, it is hypothesized that small fructans and RFOs act as phloem-mobile signaling compounds under stress. It is speculated that such underlying antioxidant and oligosaccharide signaling mechanisms contribute to disease prevention in plants as well as in animals and in humans.