Heat in Wheat: Exploit Reverse Genetic Techniques to Discover New Alleles Within the Triticum durum sHsp26 Family

Wheat breeding nowadays must address producers and consumers' desire. According to the last FAO report, a dramatic decrease in wheat production is expected in the next decades mainly due to the upcoming climate change. The identification of the processes which are triggered by heat stress and how thermotolerance develops in wheat is an active research topic. Genomic approach may help wheat breeding since it allows direct study on the genotype and relationship with the phenotype. Here the isolation and characterization of four members of the chloroplast-localized small heat shock proteins (sHSP) encoded by the Hsp26 gene family is reported. Furthermore, two high throughput TILLING (Targeting Induced Local Lesions In Genomes) approaches in vivo and in silico were used for the identification of new alleles within this family. Small heat shock proteins are known to prevent the irreversible aggregation of misfolded proteins and contribute to the acquisition of thermotolerance. Chloroplast-localized sHSPs protect the photosynthetic machinery during episodes of high temperature stress. The modulation of the newly discovered genes within the sHsp26 family has been analyzed in vivo and by the ExpVIP platform widening the abiotic stress analysis; and their involvement in the heat stress response has been demonstrated. In addition, in this study a total of 50 TILLING mutant lines have been identified. A set of KASP (Kompetitive Allele Specific PCR) markers was also developed to follow the specific mutations in the ongoing backcrosses, applicable to high throughput genotyping approaches and usable in marker assisted selection breeding programs

The expression of a bean PGIP in transgenic wheat confers increased resistance to the fungal pathogen Bipolaris sorokiniana

In several plant-pathogen interactions to overcome the barrier represented by cell wall most fungal pathogens produce a variety of hydrolytic enzymes and between them PGs are one of the first to be secreted. We demonstrate that transgenic wheat plants expressing PvPGIP2 showed a significant reduction of symptoms following the infection of Bipolaris sorokiniana suggesting that pectin hydrolysis is an important step for fungal penetration of wheat plants.In molti sistemi pianta patogeno i patogeni al fine di superare l’ostacolo rappresentato dalla parete cellulare producono degli enzimi idrolitici tra cui le Poligalatturonasi ( PG) sono tra i primi ad essere secreti. In questo lavoro dimostriamo che piante transgeniche di frumento sovraesprimenti la PvPGIP2 mostrano una significativa riduzione nella sintomatologia riscontrata in seguito ad infezione con Bipolaris sorokiniana suggerendo che l’idrolisi della pectina rappresenta uno step importante per la penetrazione e la colonizzazione dei tessuti di frumento.L'articolo é disponibile sul sito dell'editore: http://www.apsjournals.apsnet.or

Tissue specific expression of PvPGIP2 to improve wheat resistance against Fusarium graminearum

Fusarium Head Blight (FHB) is one of the most important wheat diseases caused by Fusarium spp.. The pathogen infects the spike at flowering time and causes severe yield losses and deterioration of grain quality due to the secretion of mycotoxins during infection. The understanding of the precise mode of pathogen entering and the subsequent floral tissue colonize is a crucial point to control FHB. Polygalacturonase inhibiting proteins (PGIPs) are cell wall proteins that inhibit the pectin-depolymerizing activity of polygalacturonases (PGs) secreted by pathogens. The constitutive expression of the bean PvPGIP2 limits FHB symptoms and reduces mycotoxin accumulation in wheat. To better understand which spike tissues plays a role in limiting Fusarium infection, we have produced transgenic wheat plants expressing PvPGIP2 in the endosperm or simultaneously in lemma, palea, anthers and rachis. This latter approach reduced FHB symptoms, whereas the expression of PvPGIP2 only in the endosperm did not affect FHB development, indicating that when the pathogen has reached the endosperm, inhibition of pathogen PGs ineffective to prevent fungal spread

Tissue-specific expression of PvPGIP2 to improve wheat resistance against Fusarium graminearum

Fusarium Head Blight (FHB) is one of the most important wheat diseases caused by some fungi of the genus Fusarium. The pathogen infects the spike at flowering time and causes severe yield losses and deterioration of grain quality due to the secretion of mycotoxins during infection. The understanding of the precise mode of pathogen entering and the subsequent floral tissue colonize is a crucial point to control FHB. Polygalacturonase inhibiting proteins (PGIPs) are cell wall proteins that inhibit the pectin-depolymerizing activity of polygalacturonases (PGs) secreted by microbial pathogens and insects. The constitutive expression of the bean PvPGIP2 limits FHB symptoms and reduces mycotoxin accumulation in wheat. To better understand the spike tissues that play a role in limiting Fusarium infection, we have produced transgenic wheat plants expressing PvPGIP2 or in the endosperm or simultaneously in lemma, palea, anthers and rachis. We showed that this latter approach reduced FHB symptoms caused by F. graminearum compared to control non transgenic plants. The extent of disease symptom reduction was similar to what obtained when PvPGIP2 was expressed constitutively. We showed also that different level of PvPGIP2 accumulation produced similar level of protection. Conversely, the expression of PvPGIP2 only in the endosperm did not affect FHB symptom development, indicating that when the pathogen has reached the endosperm, inhibition of the polygalacturonase (PG) activity of the pathogen is ineffective to prevent fungal spread. Probably the rich source of the endosperm tissue makes the PG activity dispensable for pathogen colonization. Alternatively, the massive growth of the fungus at this stage produces a large amount of PG that is not inhibited by the available PGIP

Can High Throughput Phenotyping Help Food Security in the Mediterranean Area?

According to the IPCC 2014 report the Mediterranean region will be affected by strong climatic changes, both in terms of average temperature and of precipitations regime. This area hosts some half a billion people and the impact on food production will be severe. To implement a climate smart agriculture paradigm and a sustainable increase of agricultural productivity different approaches can be deployed. Agriculture alone consumes 70% of the entire water available on the planet, thus the observed reduction of useful rainfall and growing costs for irrigation water may severely constrain food security. In our work we focused on two typical Mediterranean crops: durum wheat, a rainfed crop, and tomato, an irrigated one. In wheat we explored the possibility of identifying genotypes resilient to water stress for future breeding aims, while in tomato we explored the possibility of using biostimulants to increase the plant capacity of using water. In order to achieve these targets, we used high throughput phenotyping (HTP). Two traits were considered: digital biovolume, a measure based on imaging techniques in the RGB domain, and Water Use Efficiency index as calculated semi-automatically on the basis of evaporation measurements resulting in a high throughput, non-destructive, non-invasive approach, as opposed to destructive and time consuming traditional methods. Our results clearly indicate that HTP is able to discriminate genotypes and biostimulant treatments that allow plants to use soil water more efficiently. In addition, these methods based on RGB quality images can easily be scaled to field phenotyping structure USVs or UAVs

EXPRESSION OF BEAN PGIP2 UNDER CONTROL OF THE BARLEY LEM1 PROMOTER LIMITS FUSARIUM GRAMINEARUM INFECTION IN WHEAT

Fusarium Head Blight (FHB) caused by Fusarium graminearum is one of the most destructive fungal diseases of wheat worldwide. The pathogen infects the spike at flowering time and causes severe yield losses, deterioration of grain quality, and accumulation of mycotoxins. Better understanding of the means of pathogen entry and colonization of floral tissue is crucial to providing effective protection against FHB. Polygalacturonase inhibiting proteins (PGIPs) are cell wall proteins that inhibit the activity of polygalacturonases (PGs), a class of pectin-depolymerizing enzymes secreted by microbial pathogens, including Fusaria. The constitutive expression of a bean PGIP (PvPGIP2) under control of the maize Ubi1 promoter limits FHB symptoms and reduces mycotoxin accumulation in wheat grain [Janni et al. 2008 Molec. Plant Microb. Interact. 21:171]. To better understand which spike tissues play major roles in limiting F. graminearum infection, we explored the use of PvPGIP2 to defend specific spike tissues by expressing it under control of the barley Lem1 promoter [Somleva and Blechl 2005 Cer. Res. Comm. 33:665]. We show here that the expression of PvPGIP2 in lemma, palea, rachis and anthers reduced FHB symptoms caused by F. graminearum compared to symptoms in infected nontransgenic plants. However, the expression of PvPGIP2 only in the endosperm under control of a HMW-glutenin gene promoter did not affect FHB symptom development, indicating that once the pathogen has reached the endosperm, inhibition of the pathogen\u2019s PG activity is not effective in preventing its further spread

Assessment of Durum Wheat (Triticum durum Desf.) Genotypes Diversity for the Integrated Production of Bioethanol and Grains

Wheat straw is an abundant source of lignocellulosic biomass that is generally not utilized for biofuel production, nor for other uses. Recent EU renewable energy directive fosters bioethanol production through lignocellulosic sugars fermentation, but the cost of this process is an issue that often depends on biomass characteristics. Lignin is a class of three-dimensional polymers providing structural integrity of plant tissues. Its complex structure, together with hemicelluloses and uronic acids content, could affect the ability of hydrolyzing biomass to fermentable sugars. To get insights into this variation, a set of 10 durum wheat genotypes was analyzed to determine variation of straw digestibility to fermentable sugars. The results showed that the lignin content was the major factor determining the recalcitrance to enzymatic process. The analysis of Spearman's correlation indicated that the sugar released after enzymatic hydrolysis had a negative connection with the lignin content, while it was positively correlated with the culm length. The possible role of other cell wall components, such as arabinose and uronic acids, was also discussed. This work aimed at analyzing the diversity of lignocellulosic digestibility to fermentable sugars of wheat straw in a small germplasm collection. Some of the selected genotypes were characterized by high sugars digestibility and high grain yield, characteristics that could make biorefining of wheat straw profitable

In Vivo Phenotyping for the Early Detection of Drought Stress in Tomato

Drought stress imposes a major constraint over a crop yield and can be expected to grow in importance if the climate change predicted comes about. Improved methods are needed to facilitate crop management via the prompt detection of the onset of stress. Here, we report the use of an in vivo OECT (organic electrochemical transistor) sensor, termed as bioristor, in the context of the drought response of the tomato plant. The device was integrated within the plant's stem, thereby allowing for the continuous monitoring of the plant's physiological status throughout its life cycle. Bioristor was able to detect changes of ion concentration in the sap upon drought, in particular, those dissolved and transported through the transpiration stream, thus efficiently detecting the occurrence of drought stress immediately after the priming of the defence responses. The bioristor's acquired data were coupled with those obtained in a high-throughput phenotyping platform revealing the extreme complementarity of these methods to investigate the mechanisms triggered by the plant during the drought stress event