HighlightRoot exudate metabolite profiling suggests antagonistic roles for individual coumarins during phosphate and iron deficiency. Oligolignol accumulation and root lignification indicate impaired oligolignol polymerization in local phosphate deficiency response mutants.

Plants face varying nutrient conditions, to which they have to adapt to. Adaptive responses are nutrient-specific and strategies to ensure supply and homeostasis for one nutrient might be opposite to another one, as shown for phosphate (Pi) and iron (Fe) deficiency responses, where many genes are regulated in an opposing manner. This was also observed on the metabolite levels. Whereas root and exudate levels of catechol-type coumarins, phenylpropanoid-derived 2-benzopyranones, which facilitate Fe acquisition, are elevated after Fe deficiency, they are decreased after Pi deficiency. Exposing plants to combined Pi and Fe deficiency showed that the generation of coumarin profiles in Arabidopsis thaliana roots by Pi deficiency considerably depends on the availability of Fe. Similarly, the effect of Fe deficiency on coumarin profiles is different at low compared to high Pi availability. These findings suggest a fine-tuning of coumarin profiles, which depends on Fe and Pi availability. T-DNA insertion lines exhibiting aberrant expression of genes involved in the regulation of Pi starvation responses (PHO1, PHR1, bHLH32, PHL1, SPX1) and Fe starvation responses (BRUTUS, PYE, bHLH104, FIT) were used to analyze the regulation of the generation of coumarin profiles in Arabidopsis thaliana roots by Pi, Fe, and combined Pi and Fe deficiency. The analysis revealed a role of several Fe-deficiency response regulators in the regulation of Fe and of Pi deficiency-induced coumarin profiles as well as for Pi deficiency response regulators in the regulation of Pi and of Fe deficiency-induced coumarin profiles. Additionally, the regulation of Fe deficiency-induced coumarin profiles by Fe deficiency response regulators is influenced by Pi availability. Conversely, regulation of Pi deficiency-induced coumarin profiles by Pi deficiency response regulators is modified by Fe availability.

Concurrent suboptimal supply of several nutrients requires the coordination of nutrient-specific transcriptional, phenotypic, and metabolic changes in plants in order to optimize growth and development in most agricultural and natural ecosystems. Phosphate (Pi) and iron (Fe) deficiency induce overlapping but mostly opposing transcriptional and root growth responses in Arabidopsis thaliana. On the metabolite level, Pi deficiency negatively modulates Fe deficiency-induced coumarin accumulation, which is controlled by Fe as well as Pi deficiency response regulators. Here, we report the impact of Fe availability on seedling growth under Pi limiting conditions and on Pi deficiency-induced accumulation of amino acids and organic acids, which play important roles in Pi use efficiency. Fe deficiency in Pi replete conditions hardly changed growth and metabolite profiles in roots and shoots of Arabidopsis thaliana, but partially rescued growth under conditions of Pi starvation and severely modulated Pi deficiency-induced metabolic adjustments. Analysis of T-DNA insertion lines revealed the concerted coordination of metabolic profiles by regulators of Fe (FIT, bHLH104, BRUTUS, PYE) as well as of Pi (SPX1, PHR1, PHL1, bHLH32) starvation responses. The results show the interdependency of Pi and Fe availability and the interplay between Pi and Fe starvation signaling on the generation of plant metabolite profiles.

The genus Ocimum, (family Lamiaceae), displays great variability. Prevalence of cross pollination, polyploidy and interspecific hybridization has complicated its taxonomy, making its systematic study difficult. This study investigated the morphological and biochemical variability among 18 ecotypes collected from different parts of the Assam state, India. Considerable diversity was found using all the approaches. The quantitative morphological parameters showed wide variability, not always co-relating with their geographical distances. The Euclidean distance ranged between 6.06 (between the closest accessions) and 59.00 (between the most distant accessions). Phylogenetic analysis divided the accessions into two major clusters sharing approx. 76% identity, and a minor cluster (with three accessions) sharing only approx. 65% identity with the other two. A great deal of diversity was found in the qualitative characters too; that divided the ecotypes into two to five groups. The biochemical characters also revealed wide polymorphism; the distance varied from 1.690 to 58.574. Similar to the morphological characters, the biochemical parameters too did not always correlate with geographical distances. The phylogenetic mapping divided the accessions into two major clusters, sharing approx. 80% similarity. Further work will be needed to correlate the distance based on the morphological and the biochemical characters. (Omidbaigi et al. 2010, Carovic-Stanko et al. 2011. However, there is little information available regarding the plant's diversity in India and in Asia; there is confusion regarding even its genome structure. The northeastern part of India, including the state of Assam, being a biodiversity hotspot, would be a good start point to study the diversity of the plant in the country as well as in the region. To our knowledge, this is the first report on the categorization of the morphological and biochemical parameters of the plant. MATERIALS AND METHODS Plant Materials and Growth ConditionsThe plant materials were collected from 18 different districts of Assam and were named as accession (Acc) #1 to accession #18 (Table 1; Fig 1). Seeds were also collected for all the ecotypes, and were germinated in laboratory on moist filter paper in Assam Agricultural University (AAU), Jorhat. The seedlings were grown in the potting mixture prepared by mixing soil, sand and dried manure in the ratio of 2:1:1 v/v, and the plants were maintained in typical greenhouse conditions (16/8 hours of light/dark cycle and 22-25°C temperature) in the AAU facility. The morphological data were recorded at the vegetative (150 day-old) stage of the plants for the leaf and the stem characters; the inflorescence characters were taken at the reproductive stage, at the 200 day-old plants. For collection of the biochemical data, leaf samples were collected at the same stage and were processed for isolation and/ or quantification of the parameters. Morphological ParametersDefined descriptors are not available in tulsi. Therefore, based on t...

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