Does genetic diversity in plants matter? An environmental metabolomic approach
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ABA increases the expression of plasma membrane aquaporin (PIP) genes, it is not clear if it has a long-lasting effect on Lp r and to what extent ABA-related changes in leaf growth rate are due to differences in Lp r . We addressed these questions with a series of transformant maize lines deregulated in the expression of the VP14 gene encoding NCED, a key enzyme of ABA synthesis. One sense (S) and three antisense (AS) lines with contrasting ABA biosynthesis capacities were analysed in moderate water deficit. As expected, increased ABA synthesis caused stomatal closure and increased leaf water potential. The protein contents of 3 PIP aquaporins were strongly increased in roots and leaves in S plants, and decreased in AS plants. This resulted in large differences in Lp r measured on excised root systems, with 4-fold values in S compared with AS plants, and an intermediate Lp r in WT. The hydraulic conductance of transpiring whole plants was also largely affected. The recoveries of leaf elongation rate and leaf water potential after rewatering were quicker in S and slower in AS plants than in WT. A model of water transfer accounted for these changes and suggested an important role for both root and leaf hydraulic conductances in the recovery rates. Overall, these results suggest that ABA has long-lasting effects on both plant hydraulic and stomatal conductances, which contribute to maintain a favourable plant water status. doi:10.1016/j.cbpa.2008.04.543 P3.43 Growth and influence of defoliation in terrestrial orchids, Anacamptis morio and Serapia lingua A. Darkwa, P. Scott (University of Sussex) Growing temperate orchids has always been difficult since the knowledge of understanding the physiology of these plants is lacking. We studied the seasonal life cycle of a United Kingdom orchid species Anacamptis morio. We also examined the effects of experimental defoliation on both this orchid species and another species, Serapia lingua. The plants were assessed on three defoliation levels (0%, 50%, 100% removal of total leaf area). Leaf removal from plants was done twice, in early stage of growth and during the period of tuber initiation. The seasonal growth indicated that the old tuber was not accustomed to support aerial growth throughout the winter. While the extent of the leaf canopy was not supported by the old tuber, there was yet a close relationship between tuber size and final canopy. Hence, it suggests that an orchid must be very sensitive to any damage to the canopy in the early stages of its growing season through grazing. A. morio however showed a higher leaf re-growth capacity and resilience to the simulated herbivory. Flowering and tuber production of the defoliated plants were not significantly different from the non-defoliated. On the other hand, defoliation significantly affected flowering and growth below the ground in S. lingua. The complete removal of leaves from plants in February resulted in no flowering. Key words: Terrestrial orchids, Defoliation, Herbivory, Tuber, Anacamptis morio, Serapia lingua doi:10.1016/j.cbpa.2008.04.544 P3.44 Influence of depth of planting on stolon and tuber formation in Serapia lingua A. Darkwa, P. Scott (University of Sussex) While several terrestrial orchids produce spreading rhizomes others form tubers. The tuber initiates from a stolon which can control the depth of the next year's tuber. We investigated the effect of planting depth on stolon and tuber formation in the terrestrial orchid Serapia lingua. The study showed that the depth of planting had influence on stolon length and consequently, the position of the tuber in the soil. Deep planting resulted in the production of short stolons and affected the number of tubers and the final yield. However, there was no correlation between the length and weight of the stolon during its formation and the weight of the final tuber. Key words: Planting depth, Terrestrial orchid, Stolon, Tuber, Serapia lingua doi:10.1016/j.cbpa.2008.04.545 P3.45 Activation of the TAS3-derived tasiRNA pathway in the root system of Arabidopsis thaliana A. Maizel (CNRS Institut des Sciences du Végétal); E. Marin (LBDP CEA Cadarache); A. Herz (LBDP CEA Cadarache); M. Crespi (CNRS Institut des Sciences du Végétal) Plant and animals use small RNAs (microRNAs and siRNAs) as guide for post-transcriptional and epigenetic regulation. In plants, miRNAs and trans-acting siRNA (tasiRNA) result from different biogenesis pathways but both interact with target transcripts to direct their cleavage. Four tasiRNA gene families (TAS1-4) are known in Ar- abidopsis thaliana. TAS gene transcripts are cleaved by miRNAs; the cleavage products are copied into dsRNA by RDR6, and diced into tasiRNAs by DCL4. Biogenesis of TAS3-derived tasiRNAs involves miR390 and they target mRNAs encoding AUXIN RESPONSE FACTORs ARF3/ETTIN and ARF4. Specific degradation of ARF3 in the leaves by TAS3-derived tasiRNA is critical for leaf development and phase transition. In a screen for large non-protein coding RNAs in Arabidopsis using a dedicated micro-array, we identified that TAS3a gene is also expressed in root tissues, in particular at the secondary root branching points. Using reporter constructs for TAS3a and miR390 loci, as well as analysis of the accumulation of their derived RNAs, we have characterized the expression pattern of the TAS3 pathway during root development. We present evidence that this pathway might be linked to the architecture of the root system. doi:10.1016/j.cbpa.2008.04.546 P3.46 Does genetic diversity in plants matter? An environmental metabolomic approach K. Field, J. Lake (University of Sheffield) Genetic diversity is thought to play an essential role in the survival of plant populations in dynamic environments. Using a novel metabolic approach combined with morphological trait screening, the plasticity of four distinct genotypes of a Carex caryophyllea (spring sedge) population to soil nutrient status was investigated. C. caryophyllea inhabits areas if natural heterogeneity. We report that this technique identified unique metabolic and morphological S197 Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S186–S198
Transcript of Does genetic diversity in plants matter? An environmental metabolomic approach
ABA increases the expression of plasma membrane aquaporin (PIP)genes, it is not clear if it has a long-lasting effect on Lpr and to whatextent ABA-related changes in leaf growth rate aredue to differences inLpr. We addressed these questions with a series of transformant maizelines deregulated in the expression of the VP14 gene encoding NCED, akey enzyme of ABA synthesis. One sense (S) and three antisense (AS)lines with contrasting ABA biosynthesis capacities were analysed inmoderate water deficit. As expected, increased ABA synthesis causedstomatal closure and increased leaf water potential. The proteincontents of 3 PIP aquaporins were strongly increased in roots andleaves in S plants, and decreased in AS plants. This resulted in largedifferences in Lprmeasured on excised root systems, with 4-fold valuesin S compared with AS plants, and an intermediate Lpr in WT. Thehydraulic conductance of transpiring whole plants was also largelyaffected. The recoveries of leaf elongation rate and leaf water potentialafter rewatering were quicker in S and slower in AS plants than inWT.A model of water transfer accounted for these changes and suggestedan important role for both root and leaf hydraulic conductances in therecovery rates. Overall, these results suggest that ABA has long-lastingeffects on both plant hydraulic and stomatal conductances, whichcontribute to maintain a favourable plant water status.
doi:10.1016/j.cbpa.2008.04.543
P3.43Growth and influence of defoliation in terrestrial orchids,Anacamptis morio and Serapia lingua
A. Darkwa, P. Scott (University of Sussex)
Growing temperate orchids has always been difficult since theknowledge of understanding the physiology of these plants is lacking.We studied the seasonal life cycle of a United Kingdom orchid speciesAnacamptis morio. We also examined the effects of experimentaldefoliation on both this orchid species and another species, Serapialingua. The plants were assessed on three defoliation levels (0%, 50%,100% removal of total leaf area). Leaf removal from plants was donetwice, in early stage of growth and during the period of tuber initiation.The seasonal growth indicated that the old tuberwas not accustomed tosupport aerial growth throughout the winter. While the extent of theleaf canopy was not supported by the old tuber, there was yet a closerelationship between tuber size and final canopy. Hence, it suggests thatanorchidmustbe very sensitive to anydamage to the canopy in theearlystages of its growing season through grazing. A. morio however showeda higher leaf re-growth capacity and resilience to the simulatedherbivory. Flowering and tuber production of the defoliated plantswere not significantly different from the non-defoliated. On the otherhand, defoliation significantly affected flowering and growth below theground in S. lingua. The complete removal of leaves from plants inFebruary resulted in no flowering.
Key words: Terrestrial orchids, Defoliation, Herbivory, Tuber,Anacamptis morio, Serapia lingua
doi:10.1016/j.cbpa.2008.04.544
P3.44Influence of depth of planting on stolon and tuber formation inSerapia lingua
A. Darkwa, P. Scott (University of Sussex)
While several terrestrial orchids produce spreading rhizomesothers form tubers. The tuber initiates from a stolon which cancontrol the depth of the next year's tuber. We investigated the effectof planting depth on stolon and tuber formation in the terrestrialorchid Serapia lingua. The study showed that the depth of plantinghad influence on stolon length and consequently, the position ofthe tuber in the soil. Deep planting resulted in the production ofshort stolons and affected the number of tubers and the finalyield. However, there was no correlation between the length andweight of the stolon during its formation and the weight of the finaltuber.
Key words: Planting depth, Terrestrial orchid, Stolon, Tuber, Serapialingua
doi:10.1016/j.cbpa.2008.04.545
P3.45Activation of the TAS3-derived tasiRNA pathway in the rootsystem of Arabidopsis thaliana
A. Maizel (CNRS Institut des Sciences du Végétal); E. Marin (LBDP CEACadarache); A. Herz (LBDP CEA Cadarache); M. Crespi (CNRS Institutdes Sciences du Végétal)
Plant and animals use small RNAs (microRNAs and siRNAs) asguide for post-transcriptional and epigenetic regulation. In plants,miRNAs and trans-acting siRNA (tasiRNA) result from differentbiogenesis pathways but both interact with target transcripts to directtheir cleavage. Four tasiRNA gene families (TAS1-4) are known in Ar-abidopsis thaliana. TAS gene transcripts are cleaved by miRNAs; thecleavage products are copied into dsRNA by RDR6, and diced intotasiRNAs by DCL4. Biogenesis of TAS3-derived tasiRNAs involvesmiR390 and they target mRNAs encoding AUXIN RESPONSE FACTORsARF3/ETTIN and ARF4. Specific degradation of ARF3 in the leaves byTAS3-derived tasiRNA is critical for leaf development and phasetransition. In a screen for large non-protein coding RNAs in Arabidopsisusing a dedicated micro-array, we identified that TAS3a gene is alsoexpressed in root tissues, in particular at the secondary root branchingpoints. Using reporter constructs for TAS3a and miR390 loci, as well asanalysis of the accumulation of their derived RNAs, we havecharacterized the expression pattern of the TAS3 pathway duringroot development. We present evidence that this pathway might belinked to the architecture of the root system.
doi:10.1016/j.cbpa.2008.04.546
P3.46Does genetic diversity in plants matter? An environmentalmetabolomic approach
K. Field, J. Lake (University of Sheffield)
Genetic diversity is thought to play an essential role in thesurvival of plant populations in dynamic environments. Using anovel metabolic approach combined with morphological traitscreening, the plasticity of four distinct genotypes of a Carexcaryophyllea (spring sedge) population to soil nutrient status wasinvestigated.
C. caryophyllea inhabits areas if natural heterogeneity. We reportthat this technique identified unique metabolic and morphological
S197Abstracts / Comparative Biochemistry and Physiology, Part A 150 (2008) S186–S198
phenotypes within the population under various nutrient treat-ments. This study shows the ability of metabolomics to identify highlevels of plasticity within this species.
The importance of our findings is highly relevant to plantpopulations experiencing environmental fluctuation as a result ofanthropogenic effects and that such genotypic plasticity may becritical to the survival of plant populations under predicted scenariosof climate change.
doi:10.1016/j.cbpa.2008.04.547
P3.47mRNA Translation is a Component of Plant RNA silencing
E. Lanet (CEA-NRS/University Aix-Marseille); E. Delannoy (ARC Centerof Excellence); R. Sormanil (CEA-NRS/University Aix-Marseille/INRA);P. Crété (CEA-NRS/University Aix-Marseille); C. Robaglia (CEA-CNRS/University Aix-Marseille)
MicroRNAs (miRNAs) regulate gene expression post-transcription-ally through RNA silencing, a conservedmechanism in plants, animals,
and other eukaryotes. The common paradigm is that most animalmiRNAs affect gene expression by blocking mRNAs translation whilemost plant miRNAs trigger mRNAs cleavage prior to translation.
miRNAs and their translated mRNA target have been shown to beassociated with polysomes in several organisms like Caenorhabditiselegans, Drosophila melanogaster or mammalian cells. How miRNAs-ribonucleoprotein complexes (miRNPs) repress translation remainsunclear, although it is thought that they exert their effects through avariety of mechanisms. In plants, few studies suggest that RNAsilencing may also involve translational control but molecularevidences of interaction between the RNA silencing and translationalmachinery are missing.
In this work we used polysomes fractionation to investigate thelink between miRNPs and the translational machinery in Arabidopsisthaliana. Our data indicate that plant miRNPs that target translatablemRNAs are to a large extent associated with polysomes. Furthermore,we used mutants affected in RNA silencing pathway to identify theproteins involved in this mechanism.
We will discuss our data about RNA silencing and translation inplants in the context of eukaryotes evolution.
doi:10.1016/j.cbpa.2008.04.628
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