The carbon economics of vegetative phase change: why plants make juvenile and adult leaves

Across plant species and biomes, a conserved set of leaf traits govern the economic strategy used to assimilate and invest carbon. As plants age, they face new challenges that may require shifts in this leaf economic strategy. In this study, we investigate the role of the developmental transition, vegetative phase change (VPC), in altering carbon economics as plants age. We used overexpression of miR156, the master regulator of VPC, to modulate the timing of VPC in Populus tremula x alba, Arabidopsis thaliana and Zea mays to understand the impact of this transition on leaf economic traits, including construction cost, payback time, and return on investment. Here we find that VPC regulates the shift from a low-cost, quick return juvenile strategy to a high-cost, high-return adult strategy. The juvenile strategy is advantageous in light-limited conditions, whereas the adult strategy provides greater returns in high-light. The transition between these strategies is correlated with the developmental decline in the level of miR156, suggesting that is regulated by the miR156/SPL pathway. Our results provide an eco-physiological explanation for the existence of juvenile and adult leaf types, and suggest that natural selection for these alternative economic strategies could be an important factor in plant evolution.

Interactionsbetween of Orius sp. (Heteroptera: Anthocoridae) and Amblyseius (Typhlodromips) Swirskii (Athias-Henriot) (Acari: Phytoseiidae) for biological control of Thirps palmi karny (Thysanoptera: Thripidae) on muskmelon

In this study, we examined biological control Thirps palmi Karny of a predatory mite Amblyseius (Typhlodromips) swirskii (AthiasHenriot), the anthocorid bug Orius sp. and combination of Amblyseius swirskii and Orius sp. The experiments in laboratory condition showed that combination of these two species have the ability to prey consumtion is higher than using only predator (Orius sp. or Amblyseius swirskii). The fecundity of Orius sp. in the absence of Amblyseius swirskii (the total number of eggs/ females = 45.5 ± 2.25 eggs, the oviposition period = 16.49 ± 0.5 days) were higher than in the presence of Amblyseius swirskii (the total number of eggs/ females = 35.6 ± 2.33 eggs, the oviposition period = 13.1 ± 0.63 days). Similar with Amblyseius swirskii, the fecundity of Amblyseius swirskii in the absence of Orius sp. (the total number of eggs/females = 35.57 ± 3.62 eggs, the oviposition period = 21.33 ± 0.7 days) were higher than in the presence of Amblyseius swirskii (the total number of eggs/ females = 24.1 ± 1.67 eggs, the oviposition period = 13 ± 1.43 days). In the greenhouse with area of 300m2, the experiments were conducted when used two-predator were average aduts (Orius sp. were 3.47 adult/ leaf, A. swirskii were 6.96 adult/ leaf) were aqual as release of only Orius sp. (average adult = 3.81 adult/ leaf) or only Amblyseius swirskii (average adult = 6.49 adult/ leaf). This study also provides further evidence that intraguild predation does not necessarily have negative effects on biological control.

Anatomy and transcription dynamics of wheat ribosomal RNA loci revealed by optical mapping and RNA sequencing

Three out of four RNA components of ribosomes are encoded by 45S rDNA loci, whose transcripts are processed into 18S, 5.8S and 26S ribosomal RNAs. The loci are organized as long head-to-tail tandem arrays of nearly identical units spanning over several megabases of sequence. Due to this peculiar structure, the exact copy number, sequence composition and expression status of the 45S rDNA remain elusive even in the genomics era, especially in complex polyploid genomes harbouring multiple loci. We employed a novel approach to study rDNA loci in polyploid wheat, comprising chromosome flow sorting, optical mapping and high-throughput rRNA sequencing. This enabled unbiased quantification of rDNA units in particular arrays. Total number of tandemly organised units in wheat genome was 4390, with 64.1, 31.4, 3.9 and 0.7% located in short arms of wheat chromosomes 6B, 1B, 5D and 1A, respectively. Optical maps revealed high regularity of tandem repeats in 1B and 5D, while the 6B array showed signatures of non-rDNA sequences invasions; 1A locus harbored highly rearranged repeats with many irregularities. At the expression level, only 1B and 6B loci contributed to transcription at roughly 2:1 ratio. The 1B:6B ratio varied among five analysed tissues (embryo, coleoptile, root tip, primary leaf, adult leaf), being the highest (2.64:1) in adult leaf and lowest (1.72:1) in coleoptile. In conclusion, a fine genomic organisation and tissue-specific expression of wheat rDNA loci was deciphered, for the first time, in a complex polyploid species. The results are discussed in the context of rDNA evolution and expression.

Transcriptomic network analyses shed light on the regulation of cuticle development in maize leaves

Plant cuticles are composed of wax and cutin and evolved in the land plants as a hydrophobic boundary that reduces water loss from the plant epidermis. The expanding maize adult leaf displays a dynamic, proximodistal gradient of cuticle development, from the leaf base to the tip. Laser microdissection RNA Sequencing (LM-RNAseq) was performed along this proximodistal gradient, and complementary network analyses identified potential regulators of cuticle biosynthesis and deposition. A weighted gene coexpression network (WGCN) analysis suggested a previously undescribed function for PHYTOCHROME-mediated light signaling during the regulation of cuticular wax deposition. Genetic analyses reveal thatphyB1 phyB2double mutants of maize exhibit abnormal cuticle composition, supporting the predictions of our coexpression analysis. Reverse genetic analyses also show thatphymutants of the mossPhyscomitrella patensexhibit abnormal cuticle composition, suggesting an ancestral role for PHYTOCHROME-mediated, light-stimulated regulation of cuticle development during plant evolution.

Pengaruh Ekstrak Rebusan Daun Tithonia diversifolia (Hemsl.) A. Gray Terhadap Kadar Glukosa Darah

Tithonia diversifolia is a plant that has the potential to reduce blood glucose levels that is crucial in Diabetes Mellitus therapy. This study aims to determine the active compounds contained in the extract of T. diversifolia leaves decoction, the effect of decoction extract on the reduction of blood glucose, and the most effective decoction extract to reduce blood glucose levels as well. The study used a Completely Randomized Design (CRD) with the research treatment groups, namely: Kn = normal control (normal mice and not given leaves decoction extract), Ka = STZ control (DM mice, which are normal mice induced by 65mg/Kg of STZ), Kp = treatment control (normal mice given leaf decoction extract) , P1 = DM + mice were given young leaf decoction extract, P2 = DM + mice were given a mixture of young leaf and adult leaf decoction extract, P3 = DM + mice were given adult leaf decoction extract. The leaves used for decoction were 1-6 leaves from the shoots. The analysis of T. diversifolia leaves decoction compounds is using the visible spectrophotometers for tannins, phenols and flavonoids and GC-MS for terpenoid analysis. The result found that Tithonia diversifolia leaves decoction extracts contain tannins, flavonoids and phenols, while terpenoids are not detected. The leaves decoction extracts of T. diversifolia influenced the decreases in blood glucose levels of DM mice, especially the decoction extract of adult leaves which reduced blood glucose levels to 71.16%.

Network analyses implicate a role for PHYTOCHROME-mediated light signaling in the regulation of cuticle development in plant leaves

Plant cuticles are composed of wax and cutin, and evolved in the land plants as a hydrophobic boundary that reduces water loss from the plant epidermis. The expanding maize adult leaf displays a dynamic, proximodistal gradient of cuticle development, from the leaf base to the tip. Laser microdissection RNA Sequencing (LM-RNAseq) was performed along this proximodistal gradient, and complementary network analyses identified potential regulators of cuticle biosynthesis and deposition. Correlations between cuticle development and cell wall biosynthesis processes were identified, as well as evidence of roles for auxin and brassinosteroids. In addition, our network analyses suggested a previously undescribed function for PHYTOCHROME-mediated light signaling during cuticular wax deposition. Genetic analyses reveal that the phyB1 phyB2 double mutant of maize exhibits abnormal cuticle composition, supporting predictions of our coexpression analyses. Reverse genetic analyses also show that phy mutants of the moss Physcomitrella patens exhibit abnormal cuticle composition, suggesting a role for light-stimulated development of cuticular waxes during plant evolution.

Constructing functional cuticles: analysis of relationships between cuticle lipid composition, ultrastructure and water barrier function in developing adult maize leaves

Background and Aims Prior work has examined cuticle function, composition and ultrastructure in many plant species, but much remains to be learned about how these features are related. This study aims to elucidate relationships between these features via analysis of cuticle development in adult maize (Zea mays L.) leaves, while also providing the most comprehensive investigation to date of the composition and ultrastructure of adult leaf cuticles in this important crop plant. Methods We examined water permeability, wax and cutin composition via gas chromatography, and ultrastructure via transmission electron microscopy, along the developmental gradient of partially expanded adult maize leaves, and analysed the relationships between these features. Key Results The water barrier property of the adult maize leaf cuticle is acquired at the cessation of cell expansion. Wax types and chain lengths accumulate asynchronously over the course of development, while overall wax load does not vary. Cutin begins to accumulate prior to establishment of the water barrier and continues thereafter. Ultrastructurally, pavement cell cuticles consist of an epicuticular layer, and a thin cuticle proper that acquires an inner, osmiophilic layer during development. Conclusions Cuticular waxes of the adult maize leaf are dominated by alkanes and alkyl esters. Unexpectedly, these are localized mainly in the epicuticular layer. Establishment of the water barrier during development coincides with a switch from alkanes to esters as the major wax type, and the emergence of an osmiophilic (likely cutin-rich) layer of the cuticle proper. Thus, alkyl esters and the deposition of the cutin polyester are implicated as key components of the water barrier property of adult maize leaf cuticles.

A new species of Medinodexia Townsend (Diptera: Tachinidae) from Japan, with a discussion on phylogenetic implications of the female postabdomen in Blondeliini

Medinodexia japonica sp. nov. is described from Japan and an adult leaf beetle, Aulacophora nigripennis Motschulsky (Coleoptera: Chrysomelidae), is recorded as its host. A piercing-type ovipositor is one of the characteristics of the genus Medinodexia Townsend, but it is also found in other blondeliine genera. To evaluate the structural differences of the piercing-type ovipositor, the female postabdominal characters were examined within Blondeliini and their phylogenetic implications are briefly discussed. Females of Medinodexia are similar to those of Medina Robineau-Desvoidy for the presence of invaginations on tergite 6 and sternite 6 of the abdomen. Medinodexia exigua Shima and M. orientalis Shima are not treated here, because they are considered to belong to an undescribed genus due to differences in the male and female postabdominal characters distinguishing them from the remaining species of Medinodexia.

Transgressive segregation reveals mechanisms of Arabidopsis immunity to Brassica-infecting races of white rust (Albugo candida)

Arabidopsis thaliana accessions are universally resistant at the adult leaf stage to white rust (Albugo candida) races that infect the crop species Brassica juncea and Brassica oleracea. We used transgressive segregation in recombinant inbred lines to test if this apparent species-wide (nonhost) resistance in A. thaliana is due to natural pyramiding of multiple Resistance (R) genes. We screened 593 inbred lines from an Arabidopsis multiparent advanced generation intercross (MAGIC) mapping population, derived from 19 resistant parental accessions, and identified two transgressive segregants that are susceptible to the pathogen. These were crossed to each MAGIC parent, and analysis of resulting F2 progeny followed by positional cloning showed that resistance to an isolate of A. candida race 2 (Ac2V) can be explained in each accession by at least one of four genes encoding nucleotide-binding, leucine-rich repeat (NLR) immune receptors. An additional gene was identified that confers resistance to an isolate of A. candida race 9 (AcBoT) that infects B. oleracea. Thus, effector-triggered immunity conferred by distinct NLR-encoding genes in multiple A. thaliana accessions provides species-wide resistance to these crop pathogens.

Leaf heteroblasty in eucalypts: biogeographic evidence of ecological function

Leaves that develop on seedlings, young saplings or regenerative shoots of many eucalypt species are strikingly different in morphology from the typical leaves of more mature plants; a developmental pattern known as heteroblasty. We measured dimorphism between juvenile and adult leaves in shape and size, leaf mass per unit area, and vein frequency in a continent-wide sample of Angophora, Corymbia and Eucalyptus species. We tested whether heteroblasty in this group is an adaptation to shading by comparing the degree of juvenile–adult leaf dimorphism with the canopy closure (measured by the leaf area index) of the habitat in which species occurred. No pattern emerged for heteroblasty in leaf shape and size or leaf mass per unit area, but there was a significant relationship (accounting for phylogenetic relationships) between the degree of juvenile–adult dimorphism in vein frequency and habitat leaf area index. Juvenile leaves tended to have more widely spaced veins than adult leaves of the same species, in regions with more closed vegetative canopies. This evidence suggests that eucalypt heteroblasty is, at least in part, a hydraulic adaptation to the different conditions faced by younger and older plants in higher productivity regions with denser vegetation.