We investigated how water transport capacity, wood density and wood anatomy were related to leaf photosynthetic traits in two lowland forests in Panama. Leaf-specific hydraulic conductivity (k L ) of upper branches was positively correlated with maximum rates of net CO 2 assimilation per unit leaf area (A area ) and stomatal conductance (g s ) across 20 species of canopy trees. Maximum k L showed stronger correlation with A area than initial k L suggesting that allocation to photosynthetic potential is proportional to maximum water transport capacity. Terminal branch k L was negatively correlated with A area /g s and positively correlated with photosynthesis per unit N, indicating a trade-off of efficient use of water against efficient use of N in photosynthesis as water transport efficiency varied. Specific hydraulic conductivity calculated from xylem anatomical characteristics (k theoretical ) was positively related to A area and k L , consistent with relationships among physiological measurements. Branch wood density was negatively correlated with wood water storage at saturation, k L , A area , net CO 2 assimilation per unit leaf mass (A mass ), and minimum leaf water potential measured on covered leaves, suggesting that wood density constrains physiological function to specific operating ranges. Kinetic and static indices of branch water transport capacity thus exhibit considerable co-ordination with allocation to potential carbon gain. Our results indicate that understanding tree hydraulic architecture provides added insights to comparisons of leaf level measurements among species, and links photosynthetic allocation patterns with branch hydraulic processes.

No abstract

No abstract

No abstract

No abstract

No abstract

Age affects the production of secondary metabolites, but how developmental cues regulate secondary metabolism remains poorly understood. Annatto (Bixa orellana L.) is a source of bixin, an apocarotenoid used in the world's food industry worldwide. Understanding how age-dependent mechanisms control bixin biosynthesis is of great interest for plant biology and for pharmaceutical, cosmetic, and textile industries. Here, we used genetic and molecular tools to unravel the role of the annatto age regulated miRNA156 (miR156) targeted SQUAMOSA PROMOTER BINDING PROTEIN LIKE (BoSPL) genes in secondary metabolism. Low expression of several BoSPL genes in miR156 overexpressing annatto plants (OE::156) impacted leaf ontogeny, reducing bixin production and increasing abscisic acid (ABA) levels. Modulation of BoCCD4;4 and BoCCD1 expression, key genes in lycopene cleavage, was associated with diverting the carbon flux from bixin to ABA, whereas upregulation of lycopene β cyclase genes implies the xanthophyll biosynthetic pathway acted as a carbon sink in OE::156 plants. Proteomic analyses revealed low accumulation of most secondary metabolite-related enzymes in OE::156 plants, suggesting that miR156 targeted BoSPLs are required to activate several annatto secondary metabolic pathways. Our findings suggest that carbon flux in B. orellana OE::156 leaves was redirected from bixin to ABA production, indicating an age-dependent leaf dynamics of bixin biosynthesis. Importantly, our study opened a new venue to future annatto breeding programs aiming to improve bixin output.

Annatto [Bixa orellana L. (Bixaceae)] is a woody plant species that can reach up to 6 meters in height, with a fast growth pattern. Annatto produces a main apocaterotenoid namely bixin, a unique natural dye. This compound is highly used in the textile, pharmaceutical and food industries, among others, making annatto an important crop in both ecological and economic aspects. Despite its relevance, there are several gaps for the understanding of its developmental processes. Perhaps one of the most interesting is the role of miR156/SPL module in its physiology. This microRNA is responsible for integrating plant physiology development through modulation of SPL transcription factors that modulate leaf morphology and anatomy, among other characteristics that may be linked to secondary metabolites production. In this particular, the miR156/SPL module regulates the biosynthesis of sesquiterpenes, flavonoids, anthocyanins, and carotenoids in higher plants. In this context, B. orellana is a promising woody species with an expressive secondary metabolism activity. Therefore, we aimed to assess phenotypic changes, plant phenology, hormonal profile, secondary metabolism, expression of developmental-linked genes, and proteome portray in overexpressing miR156 lines of B. orellana plants (OE::156). We observed new patterns in plant architecture and leaf blade features. In addition, higher IAA and ABA levels were found in OE::156 plants compared to non-transformed plants (Nt). Moreover, OE::156 plants have lower bixin content than Nt. Furthermore, CCD4 showed lower expression in contrast to higher CCD1 transcriptional levels. Besides that, the proteome showed ZEP upaccumulation in OE::156 plants, which indicates that carbons are being translocated from bixin to ABA production. Further studies are suggested to understand the role of specific secondary metabolites regulation by miR156/SPL module. Keywords: microRNA. SPL proteins. Plant development. Phase change. Proteomics.