RESUMO
During shoot development, leaves undergo various ontogenetic changes, including variation in size, shape, and geometry. Passiflora edulis (passionfruit) is a heteroblastic species, which means that it experiences conspicuous changes throughout development, enabling a morphological distinction between the juvenile and adult vegetative phases. Quantification of heteroblasty requires a practical, inexpensive, reliable, and non-destructive method, such as remote sensing. Moreover, relationships among ontogenetic changes and spectral signal at leaf level can be scaled up to support precision agriculture in passion fruit crops. In the present study, we used laboratory spectroscopic measurements (400-2500 nm) and narrowband vegetation indexes (or hyperspectral vegetation indexes - HVIs) to evaluate ontogenetic changes related to development and aging in P. edulis leaves. We also assessed leaf pigment concentration to further support the application of biochemical-related narrowband indexes. We report that 30-d-old leaves can be discriminated into developmental stages through their spectral signals. MSI (Moisture Stress Index) and NDVI750 (Normalized Difference Vegetation Index ρ750) contribute most to the variation of age (15 to 30-d-old leaves) and developmental stage (phytomer positions along the plant axis) in passionfruit leaves. PRI (Photochemical Reflectance Index) played an important role in detecting age and development alterations, including heteroblasty. A biochemical and spectral comparison of pigments revealed that spectroscopy offered potential for diagnosing phenology in P. edulis, as some narrowband indexes correlated strongly with chlorophylls and carotenoids content. Narrowband vegetation indexes are found to be a suitable tool for monitoring passionfruit crops.
Assuntos
Passiflora/crescimento & desenvolvimento , Folhas de Planta/crescimento & desenvolvimento , Análise Espectral/métodos , Carotenoides/análise , Clorofila/análiseRESUMO
BACKGROUND AND AIMS: Juvenile-to-adult phase transition is marked by changes in leaf morphology, mostly due to the temporal development of the shoot apical meristem, a phenomenon known as heteroblasty. Sugars and microRNA-controlled modules are components of the heteroblastic process in Arabidopsis thaliana leaves. However, our understanding about their roles during phase-changing in other species, such as Passiflora edulis, remains limited. Unlike Arabidopsis, P. edulis (a semi-woody perennial climbing vine) undergoes remarkable changes in leaf morphology throughout juvenile-to-adult transition. Nonetheless, the underlying molecular mechanisms are unknown. METHODS: Here we evaluated the molecular mechanisms underlying the heteroblastic process by analysing the temporal expression of microRNAs and targets in leaves as well as the leaf metabolome during P. edulis development. KEY RESULTS: Metabolic profiling revealed a unique composition of metabolites associated with leaf heteroblasty. Increasing levels of glucose and α-trehalose were observed during juvenile-to-adult phase transition. Accumulation of microRNA156 (miR156) correlated with juvenile leaf traits, whilst miR172 transcript accumulation was associated with leaf adult traits. Importantly, glucose may mediate adult leaf characteristics during de novo shoot organogenesis by modulating miR156-targeted PeSPL9 expression levels at early stages of shoot development. CONCLUSIONS: Altogether, our results suggest that specific sugars may act as co-regulators, along with two microRNAs, leading to leaf morphological modifications throughout juvenile-to-adult phase transition in P. edulis.
Assuntos
Arabidopsis , MicroRNAs , Passiflora , Regulação da Expressão Gênica de Plantas , Folhas de PlantaRESUMO
Glandular trichomes are structures with widespread distribution and deep ecological significance. In the Solanum genus, type-IV glandular trichomes provide resistance to insect pests. The occurrence of these structures is, however, poorly described and controversial in cultivated tomato (Solanum lycopersicum). Optical and scanning electron microscopy were used to screen a series of well-known commercial tomato cultivars, revealing the presence of type-IV trichomes on embryonic (cotyledons) and juvenile leaves. A tomato line overexpressing the microRNA miR156, known to promote heterochronic development, and mutants affecting KNOX and CLAVATA3 genes possessed type-IV trichomes in adult leaves. A re-analysis of the Woolly (Wo) mutant, previously described as enhancing glandular trichome density, showed that this effect only occurs at the juvenile phase of vegetative development. Our results suggest the existence of at least two levels of regulation of multicellular trichome formation in tomato: one enhancing different types of trichomes, such as that controlled by the WOOLLY gene, and another dependent on developmental stage, which is fundamental for type-IV trichome formation. Their combined manipulation could represent an avenue for biotechnological engineering of trichome development in plants.
Assuntos
Solanum lycopersicum/genética , Tricomas/genética , MicroRNAs/genética , Folhas de Planta/genética , Folhas de Planta/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismoRESUMO
Heteroblasty, the temporal development of the meristem, can produce diverse leaf shapes within a plant. Gevuina avellana, a tree from the South American temperate rainforest shows strong heteroblasty affecting leaf shape, transitioning from juvenile simple leaves to highly pinnate adult leaves. Light availability within the forest canopy also modulates its leaf size and complexity. Here we studied how the interaction between the light environment and the heteroblastic progression of leaves is coordinated in this species. We used RNA-seq on the Illumina platform to compare the range of transcriptional responses in leaf primordia of G. avellana at different heteroblastic stages and growing under different light environments. We found a steady up-regulation of SQUAMOSA PROMOTER BINDING PROTEIN LIKE (SPL), NAC, YUCCA and AGAMOUS-LIKE genes associated with increases in age, leaf complexity, and light availability. In contrast, expression of TCP, TPR and KNOTTED1 homeobox genes showed a sustained down-regulation. Additionally, genes involved in auxin synthesis/transport and jasmonate activity were differentially expressed, indicating an active regulation of processes controlled by these hormones. Our large-scale transcriptional analysis of the leaf primordia of G. avellana sheds light on the integration of internal and external cues during heteroblastic development in this species.