Biology subjects

Steed, A.

Publications and source records attributed to Steed, A..

9 recordsLinked to original sources

bioRxiv2026

Diverse Diterpenoid Phytoalexins Shape Wheat Chemical Defenses

Cereal crops rely on a wide array of specialized metabolites to defend themselves against microbial pathogens. Here, using a combination of genome-wide analysis, heterologous pathway reconstruction, structural elucidation and in planta validation, we identify two pathogen-induced diterpenoid pathways in wheat that produce diterpenoids: the new glycosylated diterpenes aspisoside A and aspisoside B, and the diterpene alcohols scutenol A and scutenol B. The pathogen-responsive nature of these pathways, together with their antimicrobial activity are consistent with a likely defensive role in wheat. These compounds are produced by two biosynthetic gene clusters, each encoding a discrete pathway, so revealing organizational separation of wheat diterpenoid-based chemical defenses. The aspisoside-producing gene cluster is syntenic with diterpenoid phytoalexin-producing clusters in rice and barley, for momilactone and hordedane biosynthesis, respectively, yet gives rise to structurally distinct phytoalexins in wheat. The scutenol cluster is syntenic with currently uncharacterized predicted biosynthetic gene clusters in barley, oat, and Brachypodium. These findings establish diterpene glycosides as a previously unrecognized component of wheat defense chemistry and provide new insights into the chemical diversification of defense-related biosynthetic gene clusters within the Poaceae.

plant biology↗

bioRxiv2025

A segment of Triticum timopheevii chromosome 3G confers type II Fusarium head blight resistance and reduces DON accumulation in wheat.

Fusarium head blight (FHB) is a major disease of small grain cereals that is particularly damaging on wheat and can result in yield losses of up to 80%. Resistance to FHB in wheat is broadly classified as resistance to initial infection (type I) or resistance to disease spread within the spike (type II). A high level of type I FHB resistance was reported in an accession of wheat wild relative Triticum timopheevii. Hexaploid wheat-T. timopheevii introgression lines carrying a segment of the short arm of chromosome 3G (Chr3G) of this accession expressed high levels of FHB resistance following spray inoculation. Further analyses of these introgression lines showed that the Chr3G segment confers a potent type II resistance, accompanied by improved grain weight retention, and reduced deoxynivalenol (DON) accumulation in grain. These results indicate that the Chr3G resistance has the potential to dramatically reduce FHB susceptibility and DON accumulation in grain in wheat cultivars. An introgression of a segment of Chr7At into the short arm of chromosome Chr7A also enhanced type II FHB resistance.

plant biology↗

bioRxiv2023

The wheat powdery mildew resistance gene Pm4 also confers resistance to wheat blast

Wheat blast, caused by the fungus Magnaporthe oryzae, threatens global cereal production since its emergence in Brazil in 1985 and recently spread to Bangladesh and Zambia. Here we demonstrate that the AVR-Rmg8 effector, common in wheat-infecting isolates, is recognised by the gene Pm4, previously shown to confer resistance to specific races of Blumeria graminis f.sp. tritici, the cause of powdery mildew of wheat. We show that Pm4 alleles differ in their recognition of different AVR-Rmg8 alleles, and some confer resistance only in seedling leaves but not spikes making it important to select for those alleles that function in both tissues. This study has identified a gene recognising an important virulence factor present in wheat blast isolates in Bangladesh and Zambia and represents an important first step towards developing durably resistant wheat cultivars for these regions.

plant biology↗

bioRxiv2022

Identification of Fusarium Head Blight resistance in Triticum timopheevii accessions and characterisation of wheat-T. timopheevii introgression lines for enhanced resistance.

A diverse panel of wheat wild relative species was screened for resistance to Fusarium head blight (FHB) by spray inoculation. The great majority of species and accessions were susceptible or highly susceptible to FHB. Accessions of Triticum timopheevii (P95-99.1-1), Agropyron desertorum (9439957) and Elymus vaillantianus (531552) were highly resistant to FHB while additional accessions of T. timopheevii were found to be susceptible to FHB. A combination of spray and point inoculation assessments over two consecutive seasons indicated that the resistance in accession P95-99.1-1 was due to enhanced resistance to initial infection of the fungus (type 1 resistance), and not to reduction in spread (type 2 resistance). A panel of wheat-T. timopheevii (accession P95-99.1-1) introgression lines was screened for FHB resistance over two consecutive seasons using spray inoculation. Most introgression lines were similar in susceptibility to FHB as the wheat recipient (Paragon) but substitution of the terminal portion of chromosome 3BS of wheat with a similar-sized portion of 3G of T. timopheevii significantly enhanced FHB resistance in the wheat background.

plant biology↗

bioRxiv2022

A wheat kinase and immune receptor form the host-specificity barrier against the blast fungus

Since emerging in Brazil in 1985, wheat blast has spread throughout South America and recently appeared in Bangladesh and Zambia. We show that two wheat resistance genes, Rwt3 and Rwt4, acting as host-specificity barriers against non-Triticum blast pathotypes encode a nucleotide-binding leucine-rich repeat immune receptor and a tandem kinase, respectively. Molecular isolation of these genes allowed us to develop assays that will ensure the inclusion of these two genes in the wheat cultivars to forestall the recurrence of blast host jumps.

plant biology↗

bioRxiv2022

Comparable human spatial memory distortions in physical, desktop virtual and immersive virtual environments

Boundaries define regions of space and are integral to episodic memories. The impact of boundaries on spatial memory and neural representations of space has been extensively studied in freely-moving rodents. But less is known in humans and many prior studies have employed desktop virtual reality (VR) which lacks the body-based self-motion cues of the physical world, diminishing the potentially strong input from path integration to spatial memory. We replicated a desktop-VR study testing the impact of boundaries on spatial memory (Hartley et al., 2004) in a physical room (2.4m x 2.4m, 2m tall) by having participants (N = 27) learn the location of a circular stool and then after a short delay replace it where they thought they had found it. During the delay, the wall boundaries were either expanded or contracted. We compared performance to groups of participants undergoing the same procedure in a laser-scanned replica in both desktop VR (N = 44) and freely-walking head mounted display (HMD) VR (N = 39) environments. Performance was measured as goodness of fit between the spatial distributions of group responses and seven modelled distributions that prioritised different metrics based on boundary geometry or walking paths to estimate the stool location. The best fitting model was a weighted linear combination of all the geometric spatial models, but an individual model derived from place cell firing in Hartley et al. 2004 also fit well. High levels of disorientation in all three environments prevented detailed analysis on the contribution of path integration. We found identical model fits across the three environments, though desktop VR and HMD-VR appeared more consistent in spatial distributions of group responses than the physical environment and displayed known variations in virtual depth perception. Thus, while human spatial representation appears differentially influenced by environmental boundaries, the influence is similar across virtual and physical environments. Despite differences in body-based cue availability, desktop and HMD-VR allow a good and interchangeable approximation for examining human spatial memory in small-scale physical environments.

neuroscience↗

bioRxiv2020

Type II Fusarium head blight susceptibility factor identified in wheat

Fusarium head blight (FHB) causes significant grain yield and quality reductions in wheat and barley. Most wheat varieties are incapable of preventing FHB spread through the rachis, but disease is typically limited to individually infected spikelets in barley. We point inoculated wheat lines possessing barley chromosome introgressions to test whether FHB resistance could be observed in a wheat genetic background. The most striking differential was between 4H(4D) substitution and 4H addition lines. The 4H addition line was similarly susceptible to the wheat parent, but the 4H(4D) substitution line was highly resistant, which suggests that there is an FHB susceptibility factor on wheat chromosome 4D. Point inoculation of Chinese Spring 4D ditelosomic lines demonstrated that removing 4DS results in high FHB resistance. We genotyped four Chinese Spring 4DS terminal deletion lines to better characterise the deletions in each line. FHB phenotyping indicated that lines del4DS-2 and del4DS-4, containing smaller deletions, were susceptible and had retained the susceptibility factor. Lines del4DS-3 and del4DS-1 contain larger deletions and were both significantly more resistant, and hence had presumably lost the susceptibility factor. Combining the genotyping and phenotyping results allowed us to refine the susceptibility factor to a 31.7 Mbp interval on 4DS. HighlightWe have identified a Type II Fusarium head blight susceptibility factor on the short arm of wheat chromosome 4D and refined its position to a 31.7 Mbp interval.

genetics↗

bioRxiv2018

Speed breeding in growth chambers and glasshouses for crop breeding and model plant research

1.To meet the challenge of feeding a growing population, breeders and scientists are continuously looking for ways to increase genetic gain in crop breeding. One way this can be achieved is through \"speed breeding\" (SB), which shortens the breeding cycle and accelerates research studies through rapid generation advancement. The SB method can be carried out in a number of ways, one of which involves extending the duration of a plants daily exposure to light (photoperiod) combined with early seed harvest in order to cycle quickly from seed to seed, thereby reducing the generation times for some long-day (LD) or day-neutral crops. Here we present glasshouse and growth chamber-based SB protocols with supporting data from experimentation with several crop species. These protocols describe the growing conditions, including soil media composition, lighting, temperature and spacing, which promote rapid growth of spring and winter bread wheat, durum wheat, barley, oat, various members of the Brassica family, chickpea, pea, grasspea, quinoa and the model grass Brachypodium distachyon. Points of flexibility within the protocols are highlighted, including how plant density can be increased to efficiently scale-up plant numbers for single seed descent (SSD) purposes. Conversely, instructions on how to perform SB on a small-scale by creating a benchtop SB growth cabinet that enables optimization of parameters at a low cost are provided. We also outline the procedure for harvesting and germinating premature wheat, barley and pea seed to reduce generation time. Finally, we provide troubleshooting suggestions to avoid potential pitfalls.

plant biology↗

bioRxiv2017

Speed breeding: a powerful tool to accelerate crop research and breeding

The growing human population and a changing environment have raised significant concern for global food security, with the current improvement rate of several important crops inadequate to meet future demand [1]. This slow improvement rate is attributed partly to the long generation times of crop plants. Here we present a method called speed breeding, which greatly shortens generation time and accelerates breeding and research programs. Speed breeding can be used to achieve up to 6 generations per year for spring wheat (Triticum aestivum), durum wheat (T. durum), barley (Hordeum vulgare), chickpea (Cicer arietinum), and pea (Pisum sativum) and 4 generations for canola (Brassica napus), instead of 2-3 under normal glasshouse conditions. We demonstrate that speed breeding in fully-enclosed controlled-environment growth chambers can accelerate plant development for research purposes, including phenotyping of adult plant traits, mutant studies, and transformation. The use of supplemental lighting in a glasshouse environment allows rapid generation cycling through single seed descent and potential for adaptation to larger-scale crop improvement programs. Cost-saving through LED supplemental lighting is also outlined. We envisage great potential for integrating speed breeding with other modern crop breeding technologies, including high-throughput genotyping, genome editing, and genomic selection, accelerating the rate of crop improvement.

plant biology↗