Carla Perrotta

Molecular genetics of heat tolerance and heat shock proteins in cereals.

Heat stress is common in most cereal-growing areas of the world. In this paper, we summarize the current knowledge on the molecular and genetic basis of thermotolerance in vegetative and reproductive tissues of cereals. Significance of heat stress response and expression of heat shock proteins (HSPs) in thermotolerance of cereal yield and quality is discussed. Major avenues for increasing thermotolerance in cereals via conventional breeding or genetic modification are outlined.

Novel durum wheat genes up-regulated in response to a combination of heat and drought stress

We report the effect of heat, drought and combined stress on the expression of a group of genes that are up-regulated under these conditions in durum wheat (Triticum turgidum subsp. durum) plants. Modulation of gene expression was studied by cDNA-AFLP performed on RNAs extracted from flag leaves. By this approach, we identified several novel durum wheat genes whose expression is modulated under different stress conditions. We focused on a group of hitherto undescribed up-regulated genes in durum wheat, among these, 7 are up-regulated by heat, 8 by drought stress, 15 by combined heat and drought stress, 4 are up-regulated by both heat and combined stress, and 3 by both drought and combined stress. The functional characterization of these genes will provide new data that could help the developing of strategies aimed at improving durum wheat tolerance to field stress.

Four members of the HSP101 gene family are differently regulated in Triticum durum Desf.

Heat shock proteins play an essential role in preventing deleterious effects of high temperatures. In many plants, HSP101 has a central role in heat stress survival. We report the isolation and characterization of four cDNAs corresponding to different members of the durum wheat HSP101 gene family. Expression analysis revealed differences in their induction. Accordingly, durum wheat HSP101 genes are differently regulated, therefore having distinct roles in stress response and thermotolerance acquisition. These findings are important for further dissection of the molecular mechanisms underlying the stress response and for understanding the functions of the HSP101 family members. This information could be important for the exploitation of specific alleles in marker assisted selection for abiotic stress resistance.

Functional, textural and sensory properties of dry pasta supplemented with lyophilized tomato matrix or with durum wheat bran extracts produced by supercritical carbon dioxide or ultrasound

A study was carried out to produce functional pasta by adding bran aqueous extract (BW) and bran oleoresin (BO) obtained using ultrasound and supercritical CO2, respectively, or a powdery lyophilized tomato matrix (LT). The bioactive compounds, hydrophilic and lipophilic antioxidant activity (HAA and LAA) in vitro, were evaluated. BW supplementation did not improve antioxidant activity, whilst LT pasta showed unconventional taste and odor. BO pasta had good levels of tocochromanols (2551μg/100g pasta f.w.) and carotenoids (40.2μg/100g pasta f.w.), and the highest HAA and LAA. The oleoresin altered starch swelling and gluten network, as evidenced by scanning electron microscopy, therefore BO pasta had structural characteristics poor compared with the control (4.8% vs. 3.2% cooking loss), although this difference did not affect significantly overall sensory judgment (74 vs. 79 for BO and control, respectively). BO supplementation was most effective for increasing antioxidant activity without jeopardizing pasta quality.

Plant Tolerance to Heat Stress: Current Strategies and New Emergent Insights

Temperatures above the optimal temperature range for plant growth and reproduction cause deleterious cellular damage, which in turn affects plant productivity. To relieve these effects, plants adapt to high temperature by activating a series of physiological and biochemical changes necessary to reestablish a new cellular homeostasis compatible with the increase in temperature. The genetic control of the heat shock (HS) response is quite complex and requires the activation of a network of genes, involved in the perception and transduction of the HS signal, which, in turn, trigger the up-regulation of other target genes. The induced genes code for proteins and enzymes (HS proteins, active oxygen detoxifying enzymes), playing a direct role in the protection of cellular and subcellular organelles or genes encoding enzymes involved in the biosynthesis of protective compatible compounds (sugars, polyols, betaines). Membrane lipid instauration, controlled by desaturase genes, is also a critical component of thermotolerance. This chapter covers the principal aspects of the plant HS response and the role of different class of genes in the acquisition of thermotolerance. The molecular breeding strategies currently available to alter genetically the level of the protective proteins, enzymes and molecules, that may ameliorate plant tolerance and productivity under high temperature stress, will be also discussed.

Secreted heat shock proteins in sunflower suspension cell cultures

Abstract Sunflower suspension cell cultures were subjected to different heat treatments and the electrophoretic patterns of heat-induced endocellular and secreted proteins were analyzed. In response to heat shock (3 h at 40°C), sunflower cells synthesized new polypeptides and secreted them into the medium, while the synthesis of other polypeptides was suppressed. Two major polypeptides of about 50 and 32 kDa were strongly induced. The two-dimensional electrophoretic analysis showed that the 32-kDa band is composed of at least four different polypeptides. Western blotting hybridizations of secreted proteins with various lectins were performed. The 32-kDa band gave a positive signal with concanavalin A.

Drought and Heat Differentially Affect XTH Expression and XET Activity and Action in 3-Day-Old Seedlings of Durum Wheat Cultivars with Different Stress Susceptibility

Heat and drought stress have emerged as major constraints for durum wheat production. In the Mediterranean area, their negative effect on crop productivity is expected to be exacerbated by the occurring climate change. Xyloglucan endotransglucosylase/hydrolases (XTHs) are chief enzymes in cell wall remodeling, whose relevance in cell expansion and morphogenesis suggests a central role in stress responses. In this work the potential role of XTHs in abiotic stress tolerance was investigated in durum wheat. The separate effects of dehydration and heat exposure on XTH expression and its endotransglucosylase (XET) in vitro activity and in vivo action have been monitored, up to 24 h, in the apical and sub-apical root regions and shoots excised from 3-day-old seedlings of durum wheat cultivars differing in stress susceptibility/tolerance. Dehydration and heat stress differentially influence the XTH expression profiles and the activity and action of XET in the wheat seedlings, depending on the degree of susceptibility/tolerance of the cultivars, the organ, the topological region of the root and, within the root, on the gradient of cell differentiation. The root apical region was the zone mainly affected by both treatments in all assayed cultivars, while no change in XET activity was observed at shoot level, irrespective of susceptibility/tolerance, confirming the pivotal role of the root in stress perception, signaling, and response. Conflicting effects were observed depending on stress type: dehydration evoked an overall increase, at least in the apical region of the root, of XET activity and action, while a significant inhibition was caused by heat treatment in most cultivars. The data suggest that differential changes in XET action in defined portions of the root of young durum wheat seedlings may have a role as a response to drought and heat stress, thus contributing to seedling survival and crop establishment. A thorough understanding of the mechanisms underlying these variations could represent the theoretical basis for implementing breeding strategies to develop new highly productive hybrids adapted to future climate scenarios.

Genetic and Molecular Evidences of the Regulation of Gene Expression during Heat Shock in Plants

In cultivated plants, as well as in wild species, there is a certain degree of variability in the pattern of Heat Shock Proteins (HSPs) induced after different types of temperature stress. In barley, this variability is too complex to correlate with the degrees of thermotolerance measured by physiological indexes such as osmotic potentials (-Ψ) or growth rates (CGR).

Isolation and Characterisation of a cDNA for a Novel Small HSP from Sunflower Suspension Cell Cultures

A full-length cDNA encoding a novel small heat shock protein (HaHSP17.9) was isolated from a cDNA library of sunflower (Helianthus annuus cv. Gloriasol). The deduced amino acid sequence exhibited high degree homology to the class I cytosolic sHSPs from other plant species, and contained all the conserved regions characteristic of this class of proteins. Northern analyses showed that the transcript homologous to HaHSP17.9 accumulates during heat shock in suspension cultured cells and in the different parts of sunflower seedlings.

Specific and General Gene Induction in Limiting Environmental Conditions

The genetic system that controls the response to environmental stress is characterized by the synthesis of generic and specific stress proteins. The geneHvhspl7, isolated fromHordeum vulgare subjected to heat shock at 40°C for 2 h, encodes a cytoplasmic low molecular weight heat shock protein (HSP) (class I). The expression of this gene was monitored in barley, maize and in transgenic tobacco and it was found to be specifically induced by heat but only barely by drought. Other genes, cloned from barley seedlings treated with ABA, most of them encoding DHN- or LEA-type proteins, showed a more specific expression in condition of drought stress. These genes have been mapped in several grasses and the map position utilized to establish the chromosomal localization of a drought related QTL. These stress inducible genes along with others isolated by different molecular genetic techniques (RDD, RDA, subtractive hybridization) could be useful “candidate genes” in the dissection of these Quantitative Traits Loci (QTLs). Stress-induced genes have been proved to be extremely powerful in RFLP analysis, because they can reveal genetic distances between cultivars adapted to different ecogeographic conditions, characterized by different water availability, and could be considered interesting descriptors of what could be termed “useful variation”.