Cold and salt stress regulates the expression and activity of a chickpea cytosolic Cu/Zn superoxide dismutase

A cDNA clone encoding a cytosolic superoxide dismutase (SOD) was isolated from a cDNA library constructed from poly(A) RNA from epicotyls of 5-day-old Cicer arietinum L. etiolated seedlings after a differential screening to select clones whose expression decreases with epicotyl growth. Analysis of its deduced amino acid sequence showed all the typical structural motifs of plant cytosolic SODs (EC 1.15.1.1.). The expression of this clone is always higher in young and growing tissues than in old and storage ones, and diminishes throughout the development of the seedlings. Cytosolic Cu/Zn-SOD activity is also higher in radicles and younger internodes. Under stress conditions only cold increases the gene expression whereas the activity is clearly raised up by a saline medium. The results are discussed in relation to the gene regulation and enzyme activity control that crop plants use to resolve the different stresses that reduce their productivity.This research was supported by grants from the Dirección General de Enseñanza Superior e Investigación Científica (DGESIC), Spain (PB98-0290) and from the Junta de Castilla y León (SA105/01)

Specific tissue proteins 1 and 6 are involved in root biology during normal development and under symbiotic and pathogenic interactions in Medicago truncatula

Specifc tissue (ST) proteins have been shown to be involved in several processes related to plant nutritional status, development, and responses to biotic agents. In particular, ST1 and ST6 are mainly expressed in roots throughout plant development. Here, we analyze where and how the expression of the genes encoding both proteins are modulated in the legume model plant Medicago truncatula in response to the plant developmental program, nodulation induced by a benefcial nitrogen-fxing bacterium (Sinorhizobium meliloti) and the defense response triggered by a pathogenic hemibiotrophic fungus (Fusarium oxysporum). Gene expression results show that ST1 and ST6 participate in the vasculature development of both primary and lateral roots, although only ST6 is related to meristem activity. ST1 and ST6 clearly display diferent roles in the biotic interactions analyzed, where ST1 is activated in response to a N2-fxing bacterium and ST6 is up-regulated after inoculation with F. oxysporum. The role of ST1 and ST6 in the nodulation process may be related to nodule organogenesis rather than to the establishment of the interaction itself, and an increase in ST6 correlates with the activation of the salicylic acid signaling pathway during the infection and colonization processes. These results further support the role of ST6 in response to hemibiotrophic fungi. This research contributes to the understanding of the complex network that controls root biology and strengthens the idea that ST proteins are involved in several processes such as primary and lateral root development, nodule organogenesis, and the plant–microbe interaction

The gene for a xyloglucan endotransglucosylase/hydrolase from Cicer arietinum is strongly expressed in elongating tissues

We have isolated a Cicer arietinum cDNA clone (CaXTH1)1 encoding a protein that belongs to the family 16 of glycosyl hydrolases and has all the conserved features of xyloglucan endotransglucosylase/hydrolases (XTH) proteins, including the presence of a highly conserved domain (DEIDFEFLG) and four Cys which suggest the potential for forming disulfide bonds. These facts indicate that CaXTH1 encodes a putative XTH. This chickpea protein showed a high level of sequence identity with group 1 XTHs that have xyloglucan endotransglucosylase (XET) activity. CaXTH1 was selected by differential screening of a cDNA library constructed using mRNA from C. arietinum polyethylene glycol (PEG) treated epicotyls, as a clone whose expression decreased when epicotyl growth was inhibited by PEG. CaXTH1 shows an expression pattern that seems to be specific for growing tissue, mostly epicotyls and the growing internodes of adult stems. CaXTH1 mRNA was not detected in any other organs of either seedlings or adult plants. CaXTH1 mRNA was abundant when epicotyls are actively growing; there was almost no expression after PEG-treatment. CaXTH1 was up-regulated by indole acetic acid (IAA) and brassinolides (BR), showing the highest transcript levels after IAA plus BR treatment. In situ hybridization study revealed that CaXTH1 is mainly expressed in epidermal cells, the target of the cell expansion process, and also in vascular tissues. The present results suggest an involvement of the putative XTH encoded by CaXTH1 in the chickpea cell expansion process.This work was supported by grants from the Dirección General de Investigación Científica y Técnica (DGICYT), Spain (BOS2002-01900) and the Junta de Castilla y León (SA124/04)

A family of β-galactosidase cDNAs related to development of vegetative tissue in Cicer arietinum

In the cell wall of Cicer arietinum epicotyls, there are a family of b-galactosidases, one of them named bIII-Gal is a b-galactosidase able to degrade cell wall pectins. The role of the remainder b-galactosidases has not been established. In this paper, we describe the cloning and expression pattern of a family of three C. arietinum b-galactosidase cDNAs (named CanBGal-1, CanBGal-4 and CanBGal-5) and we compare these results with the previously characterized CanBGal-3 cDNA clone, which encode the bIII-Gal. The shared amino acid sequence identity among the four b-galactosidase deduced proteins (named b-Gal, bIII-Gal, bIV-Gal and bV-Gal) ranged from 63% to 81%. All display the putative active site of family 35 of the glycosyl hydrolases. An unusual characteristic of one of the chickpea b-galactosidases (bI-Gal) is the presence at the C-terminus of the enzyme of a galactose binding lectin domain. The CanBGals gene expression along seedlings and adult plant could suggests different roles of their corresponding protein throughout the chickpea plant. The expression of CanBGal-5 is related to young and meristematic stages with high cell division rate, such as the meristematic hook, very young epicotyls, and apical internodes. By contrast, CanBGal-1 and -4 seem to be more strongly related to advanced stages of epicotyl growth, increasing their expression along epicotyl age, and also in basal non-elongating stem internodes. In adult plants, CanBGal-1 shows its highest expression levels in leaves, while CanBGal-4 seems to be better represented in adult roots. This is the first report about several members of the genomic family of b-galactosidases acting during development of vegetative organs.This work was supported by a Grant from the EC (CT972224) and a Grant from the Direccio´n General de Ensen˜anza Superior e Investigacio´n Cientı´fica, Spain (BOS2002-01900)

Brassinolides and IAA induce the transcription of four α-expansin genes related to development in Cicer arietinum

Four different cDNAs encoding a-expansins have been identified in Cicer arietinum (Ca-EXPA1, Ca-EXPA2, Ca-EXPA3 and Ca-EXPA4). The shared amino acid sequence similarity among the four a-expansin proteins ranged from 67 to 89%. All of them display common characteristics such as molecular mass (around 24 kDa), amino acid numbers, and also the presence of a signal peptide. The transcription pattern of chickpea a-expansin genes in seedlings and plants suggests a specific role for each of the four a-expansins in different phases of development or in different plant organs. High levels of Ca-EXPA2 transcripts coincide with maximum epicotyl and stem growth, indicating an important involvement of this particular a-expansin in elongating tissues. Ca-EXPA3 would be related to radicle development, while Ca-EXPA4 seems to be involved in pod development.A considerable increase in the level of all Ca-EXPA transcripts accompanied the indole acetic acid (IAA) plus brassinolide (BR)-induced elongation of excised epicotyl segments. This IAA + BR induction was seen even for the chickpea expansin genes whose transcription was not affected by IAA or BR alone.This work was supported by a grant from the Ministerio de Ciencia y Tecnología, Spain (BOS2002-01900) and the Junta de Castilla y León (SA124/04)

Three members of Medicago truncatula ST family are ubiquitous during development and modulated by nutritional status (MtST1) and dehydration (MtST2 and MtST3)

Abstract Background ShooT specific/Specific Tissue (ST) belong to a protein family of unknown function characterized by the DUF2775 domain and produced in specific taxonomic plant families, mainly Fabaceae and Asteraceae, with the Medicago truncatula ST family being the largest. The putative roles proposed for this family are cell elongation, biotic interactions, abiotic stress and N reserve. The aim of this work was to go deeper into the role of three M. truncatula ST proteins, namely ST1, ST2 and ST3. Our starting hypothesis was that each member of the family could perform a specific role, and hence, each ST gene would be subjected to a different type of regulation. Results The search for cis-acting regulatory elements (CREs) in silico in pST1, pST2 and pST3 promoters showed prevalence of tissue/organ specific motifs, especially root- and seed-specific ones. Light, hormone, biotic and abiotic related motifs were also present. None of these pSTs showed the same combination of CREs, or presented the same activity pattern. In general, pST activity was associated with the vascular cylinder, mainly in roots. Promoter activation was highly specific and dissimilar during reproductive development. The ST1, ST2 and ST3 transcripts accumulated in most of the organs and developmental stages analysed - decreasing with age - and expression was higher in the roots than in the aerial parts and more abundant in light-grown plants. The effect of the different treatments on transcript accumulation indicated that ST1 behaved differently from ST2 and ST3, mainly in response to several hormones and dehydration treatments (NaCl or mannitol), upon which ST1 transcript levels decreased and ST2 and ST3 levels increased. Finally, the ST1 protein was located in the cell wall whereas ST2 and ST3 were present both in the cytoplasm and in the cell wall. Conclusions The ST proteins studied are ubiquitous proteins that could perform distinct/complementary roles in plant biology as they are encoded by differentially regulated genes. Based on these differences we have established two functional groups among the three STs. ST1 would participate in processes affected by nutritional status, while ST2 and ST3 seem to act when plants are challenged with abiotic stresses related to water stress and in physiologically controlled desiccation processes such as the seed maturation

Desarrollo de una nueva práctica de laboratorio para el estudio de la importancia de la celulosa en la estructura y función de la pared celular vegetal

Memoria ID-126. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2021-2022

Effect of low temperature storage and ethylene removal on ripening and gene expression changes in avocado fruit

Changes in physiological parameters and in the RNA population from avocado (Persea americana, Mill.) fruit stored under different conditions were analyzed. Storage at low temperatures drastically reduced the respiration and ethylene production rates. Fruit softening was delayed at 7°C, while fruits at 3"C did not soften during long-term storage. Carbon dioxide levels in the atmosphere surrounding fruit treated with a commercial ethylene absorbent, were slightly depressed at 7"C and slightly higher at 3°C, as compared to storage without the absorbent. Ethylene production rates were drastically reduced by low temperatures and appeared not to be affected by ethylene absorption. Changes in the expression of several mRNAs, detected by in vitro translation of RNA during ripening at 20"C (increases in Mr 95, 72, 65, 55, 50, 41, and 40 kD and decreases in 54 and 42 kD polypeptides) were delayed or blocked at low temperatures. Under these conditions, changes in mRNAs encoding two polypeptides (Mr 80 and 42 kD) were found to be opposite those observed during normal ripening, mRNAs for other polypeptides (Mr 90, 69, 47 and 45 kD) showed variations in level depending on storage conditions. A few mRNAs were observed only during cold storage (Mr 62, 60, 58, 57, 56, and 47 kD) and could be related to cold stress or acclimation of the fruits. The results obtained suggest that the main effect of low temperatures in avocado is a delay or blockage in the expression of specific genes related to ripening. The effect of the ethylene absorbent was mainly noted in the polypeptide pattern for translated mRNAs, in which most of the changes observed for non-treated fruit were delayed.This study was supported by a Science and Technology for Development Programme, project no. STD2.0266.ES (JR), funded by EEC