Potato vacuolar acid invertase (StvacINV1) (β-fructofuranosidase; EC 3.2.1.26) has been confirmed to play an important role in cold-induced sweetening of potato tubers. However, the transcriptional regulation mechanisms of StvacINV1 are largely unknown. In this study, the 5'-flanking sequence of StvacINV1 was cloned and the cis-acting elements were predicted. Histochemical assay showed that the StvacINV1 promoter governed β-glucuronidase (GUS) expression in potato leaves, stems, roots and tubers. Quantitative analysis of GUS expression suggested that the activity of StvacINV1 promoter was suppressed by sucrose, glucose, fructose, and cold, while enhanced by indole-3-acetic acid (IAA), and gibberellic acid (GA3). Further deletion analysis clarified that the promoter regions from -118 to -551, -551 to -1021, and -1021 to -1521 were required for responding to sucrose/glucose, GA3, and IAA, respectively. These findings provide essential information regarding transcriptional regulation mechanisms of StvacINV1.

The ω-3 fatty acid desaturases (FADs) are enzymes responsible for catalyzing the conversion of linoleic acid to α-linolenic acid localized in the plastid or in the endoplasmic reticulum. In this research we report the genotypic and phenotypic variation of Italian Olea europaea L. germoplasm for the fatty acid composition. The phenotypic oil characterization was followed by the molecular analysis of the plastidial-type ω-3 FAD gene (fad7) (EC 1.14.19), whose full-length sequence has been here identified in cultivar Leccino. The gene consisted of 2635 bp with 8 exons and 5'- and 3'-UTRs of 336 and 282 bp respectively, and showed a high level of heterozygousity (1/110 bp). The natural allelic variation was investigated both by a LiCOR EcoTILLING assay and the PCR product direct sequencing. Only three haplotypes were identified among the 96 analysed cultivars, highlighting the strong degree of conservation of this gene.

Nitrosative status has emerged as a key component in plant response to abiotic stress; however, knowledge on its regulation by different environmental conditions remains unclear. The current study focused on nitrosative responses in citrus plants exposed to various abiotic stresses, including continuous light, continuous dark, heat, cold, drought and salinity. Morphological observations and physiological analysis showed that abiotic stress treatments were sensed by citrus plants. Furthermore, it was revealed that nitrosative networks are activated by environmental stress factors in citrus leaves as evidenced by increased nitrite (NO) content along with the release of NO and superoxide anion (O2(-)) in the vascular tissues. The expression of genes potentially involved in NO production, such as NR, AOX, NADHox, NADHde, PAO and DAO, was affected by the abiotic stress treatments demonstrating that NO-derived nitrosative responses could be regulated by various pathways. In addition, S-nitrosoglutathione reductase (GSNOR) and nitrate reductase (NR) gene expression and enzymatic activity displayed significant changes in response to adverse environmental conditions, particularly cold stress. Peroxynitrite (ONOO(-)) scavenging ability of citrus plants was elicited by continuous light, dark or drought but was suppressed by salinity. In contrast, nitration levels were elevated by salinity and suppressed by continuous light or dark. Finally, S-nitrosylation patterns were enhanced by heat, cold or drought but were suppressed by dark or salinity. These results suggest that the nitrosative response of citrus plants is differentially regulated depending on the stress type and underscore the importance of nitrosative status in plant stress physiology.

Alkali stress inhibits plant growth and development and thus limits crop productivity. To investigate the possible genetic basis of alkali tolerance in rice, we generated an introgressed rice line (K83) with significantly enhanced tolerance to alkali stress compared to its recipient parental cultivar (Jijing88). By using microarray analysis, we examined the global gene expression profiles of K83 and Jijing88, and found that more than 1200 genes were constitutively and differentially expressed in K83 in comparison to Jijing88 with 572 genes up- and 654 down-regulated. Upon alkali treatment, a total of 347 genes were found up- and 156 down-regulated in K83 compared to 591 and 187, respectively, in Jijing88. Among the up-regulated genes in both K83 and Jijing88, only 34 were constitutively up-regulated in K83, suggesting that both the constitutive differentially expressed genes in K83 and those induced by alkali treatment are most likely responsible for enhanced alkali tolerance. A gene ontology analysis based on all annotated, differentially expressed genes revealed that genes with expression alterations were enriched in pathways involved in metabolic processes, catalytic activity, and transport and transcription factor activities, suggesting that these pathways are associated with alkali stress tolerance in rice. Our results illuminated the novel genetic aspects of alkali tolerance in rice and established a repertory of potential target genes for biotechnological manipulations that can be used to generate alkali-tolerant rice cultivars.

Proanthocyanidins (PA) play a major role in plant protection against biotic and abiotic stresses. Moreover these molecules are known to be beneficial for human health and are responsible for astringency of foods and beverages such as wine and thus have a great impact on the final quality of the product. Genes playing a role in the PA pathway are only partially known. The amount of available transcriptomic and genetic data to select candidate genes without a priori knowledge from orthologous function increases every day. However, the methods used so far generate so many candidate genes that it is impossible to validate all of them. In this study, we used an integrative strategy based on different screening methods to select a reduced list of candidate genes. We have crossed results from different screening methods including QTL mapping and three transcriptomic studies to select 20 candidate genes, located in QTL intervals and fulfilling at least two transcriptomic screenings. This list includes three glucosyltransferases, already suspected to have a role in the PA biosynthetic pathway. Among the 17 remaining genes, we selected three genes to perform further analysis by association genetic studies. For each of these genes, we found a polymorphism linked to PA variation. The three genes (VvMybC2-L1, VvGAT-like and VvCob-like), not previously known to play a role in PA synthesis, are promising candidates for further molecular physiology studies.

Daily dynamics of leaf (KL) and soil-to-branch hydraulic conductance (KS-B) was investigated in silver birch (Betula pendula Roth.) using evaporative flux method in situ: water potential drop was measured with a pressure chamber and evaporative flux was estimated as sap flux density measured with sap flow gauges. Canopy position had a significant (P < 0.001) effect on both KL and KS-B. Upper-canopy leaves exhibited 1.7 and soil-to-branch pathway 2.3 times higher hydraulic efficiency than those for lower-canopy. KL varied significantly with time of day: KL for both upper- and lower-canopy leaves was lowest in the morning and rose gradually achieving maximal values in late afternoon (4.75 and 3.38 mmol m(-2) s(-1) MPa(-1), respectively). Relevant environmental factors affecting KL were photosynthetic photon flux density (QP), air relative humidity (RH) and air temperature (TA). KS-B started rising in the morning and reached maximum in the lower canopy (1.44 mmol m(-2) s(-1) MPa(-1)) at 1300 h and in the upper canopy (2.52 mmol m(-2) s(-1) MPa(-1)) at 1500 h, decreasing afterwards. Environmental factors controlling KS-B were ΨS and QP. The diurnal patterns of KL reflect a combination of environmental factors and endogenous rhythms. The temporal pattern of KS-B refers to daily up- and down-regulation of hydraulic conductance of water transport pathway from soil-root interface to leaves with respect to changing irradiance.

Phytoremediation is a plant based, cost effective technology to detoxify or stabilise contaminated soils. Fast growing, high biomass, perennial plants may be used not only in phytoremediation but also in energy production. Szarvasi-1 energy grass (Elymus elongatus subsp. ponticus cv. Szarvasi-1), a good candidate for this combined application, was grown in nutrient solution in order to assess its Cd, Cu, Ni, Pb and Zn accumulation and tolerance. Its shoot metal accumulation showed the order Pb < Ni < Cu ∼ Cd < Zn. In parallel with this, Pb and Ni had no or very little influence on the growth, dry matter content, chlorophyll concentration and transpiration of the plants. Cu and Cd treatment resulted in significant decreases in all these parameters that can be attributed to Fe plaque formation in the roots suggested by markedly increased Fe and Cu accumulation. This came together with decreased shoot and root Mn concentrations in both treatments while shoot Cu and Zn concentrations decreased under Cd and Cu exposure, respectively. Zn treatment had no effect or even slightly stimulated the plants. This may be due to a slight stimulation of Fe translocation and a very efficient detoxification mechanism. Based on the average 300 mg kg(-1) (dry mass) Zn concentration which is 0.03% of the shoot dry mass the variety is suggested to be classified as Zn accumulator.

Plants live in a complex environment, exposed to stresses, such as unsuitable climates, pests and pathogenic microorganisms. Pathogens are one of the most serious factors that threaten plant growth. Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is one of the most destructive diseases worldwide. Virus-induced gene silencing (VIGS) is a popular tool for the functional analysis of wheat genes, generating abundant small RNAs (sRNAs). sRNAs are key components in gene regulatory networks, silencing corresponding genes at the post-transcriptional level. In this study, we transduced pri-tae-miR159a into plant tissues using the barley stripe mosaic virus (BSMV) system, and demonstrated that vsiRNAs were generated from the same miRNAs generating sites of pri-tae-miR159a, with the function of Dicer RNase III-like classes of endonucleases (DCL4). In addition, the accumulation of vsiRNAs in wheat leaves challenged with Pst Chinese yellow rust 23 (CYR23), resulted in a resistant phenotype, and in the compatible interaction, the sporation of Pst was limited. Whereas, infection with a control construct had no effect on the resistance or susceptibility. The results of the histological observation also supported these phenotype changes. Interestingly, vsiRNAs were also involved in the interactions between wheat and Pst through the tae-miR159-mediated regulation of taMyb3 expression. Moreover, these results also supported the speculation that vsiRNAs were generated from the same sites of pri-tae-miR159a. These studies indicated that vsiRNAs from miRNAs generating sites of pri-tae-miR159a based on the BSMV system play positive roles in the wheat response to Pst through the regulation of taMyb3 expression.

Kale (Brassica oleracea var. sabellica) contains a large number of naturally occurring structurally different non-acylated and acylated flavonol glycosides as well as hydroxycinnamic acid derivatives. The objective of this study was to determine the effect of low and moderate photosynthetic active radiation (PAR) and how these levels interact with low temperature in these phenolic compounds. Juvenile kale plants were treated with PAR levels from 200 to 800 μmol m(-2) s(-1) at 5 and 10 °C under defined conditions in climate chambers. Of the investigated 20 compounds, 11 and 17 compounds were influenced by PAR and temperature, respectively. In addition, an interaction between PAR and temperature was found for eight compounds. The response of the phenolic compounds to PAR was structure-dependent. While quercetin triglycosides increased with higher PAR at 5 and 10 °C, the kaempferol triglycosides exhibited the highest concentrations at 400 μmol m(-2) s(-1). In contrast, kaempferol diglycosides exhibited the highest concentrations at increased PAR levels of 600 and 800 μmol m(-2) s(-1) at 10 °C. However, key genes of flavonol biosynthesis were influenced by temperature but remained unaffected by PAR. Furthermore, there was no interaction between the PAR level and the low temperature in the response of hydroxycinnamic acid derivatives in kale with the exception of caffeoylquinic acid, which decreased with higher PAR levels of 600 and 800 μmol m(-2) s(-1) and at a lower temperature. In conclusion, PAR and its interaction with temperature could be a suitable tool for modifying the profile of phenolic compounds.

Flavonoids and isoflavonoids participate in the signaling exchange between roots of legumes and nitrogen-fixing rhizobia and can promote division of cortical cells during nodule formation by inhibiting auxin transport. Here, we report the characterization of a member of the common bean isoflavone reductase (EC 1.3.1.45, PvIFR1) gene family, an enzyme that participates in the last steps of the biosynthetic pathway of isoflavonoids. Transcript levels of PvIFR1 were detected preferentially in the susceptible zone of roots, augmented upon nitrogen starvation and in response to Rhizobium etli inoculation at very early stages of the interaction. Knockdown of PvIFR1 mediated by RNA interference (RNAi) in common bean composite plants resulted in a reduction of shoot and root length. Furthermore, reduction of PvIFR1 mRNAs also affected growth of lateral roots after emergence, a stage in which auxins are required to establish a persistent meristem. Upon inoculation, the number of nodules formed by different strains of R. etli was significantly lower in IFR RNAi than in control roots. Transcript levels of two auxin-regulated genes are consistent with lower levels of auxin in PvIFR1 silenced roots. These results suggest a complex role of PvIFR1 during plant growth, root development and symbiosis, all processes in which auxin transport is involved.