Tomato miR156-targeted SlSBP15 represses shoot branching by modulating hormone dynamics and interacting with GOBLET and BRANCHED1b.

The miRNA156 (miR156)/SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE (SPL/SBP) regulatory hub is highly conserved among phylogenetically distinct species, but how it interconnects multiple pathways to converge to common integrators controlling shoot architecture is still unclear. Here, we demonstrated that the miR156/SlSBP15 node modulates tomato shoot branching by connecting multiple phytohormones with classical genetic pathways regulating both axillary bud development and outgrowth. miR156-overexpressing plants (156-OE) displayed high shoot branching, whereas plants overexpressing a miR156-resistant SlSBP15 allele (rSBP15) showed arrested shoot branching. Importantly, the rSBP15 allele was able to partially restore the wild-type shoot branching phenotype in the 156-OE background. rSBP15 plants have tiny axillary buds, and their activation is dependent on shoot apex-derived auxin transport inhibition. Hormonal measurements revealed that indole-3-acetic acid (IAA) and abscisic acid (ABA) concentrations were lower in 156-OE and higher in rSBP15 axillary buds, respectively. Genetic and molecular data indicated that SlSBP15 regulates axillary bud development and outgrowth by inhibiting auxin transport and GOBLET (GOB) activity, and by interacting with tomato BRANCHED1b (SlBRC1b) to control ABA levels within axillary buds. Collectively, our data provide a new mechanism by which the miR156/SPL/SBP hub regulates shoot branching, and suggest that modulating SlSBP15 activity might have potential applications in shaping tomato shoot architecture.

Development and characterization of microsatellite markers for Hebanthe eriantha (Amaranthaceae).

PREMISE OF THE STUDY: Hebanthe eriantha (Amaranthaceae) is extensively collected and used in folk medicine. Microsatellite markers were developed and characterized to investigate the genetic structure and diversity of germplasm collections of this species. METHODS AND RESULTS: Eleven highly polymorphic microsatellite markers were developed. The number of alleles observed for each locus ranged from two to eight. The observed and expected heterozygosities ranged from 0.000 to 0.808 and 0.455 to 0.851, respectively. CONCLUSIONS: These results show the utility of microsatellite loci for studies of population genetics in H. eriantha, which are important for the future conservation and cultivation of this medicinal species.

Low root PIP1-1 and PIP2 aquaporins expression could be related to reduced hydration in 'Rangpur' lime plants exposed to aluminium.

In acidic soils, aluminium (Al) occurs as Al3+, which is phytotoxic. One of the most conspicuous symptoms of Al toxicity is the root growth inhibition, which can lead to low water uptake and consequent reduction in leaf hydration and gas exchange. However, fibrous xylem vessels have been observed in roots of 'Rangpur' lime plants (Citrus limonia L.) when exposed to Al, which could affect the functioning of aquaporins, ultimately reducing their expression. We confirmed a decrease of CO2 assimilation (A), stomatal conductance (gs), transpiration (E) and relative leaf water content (RWC) in 3-month-old C. limonia plants exposed to 1480 µM Al in nutrient solution for 90 days. The estimated hydraulic conductivity from soil to the leaf (KL) and leaf water potential (Ψw) also showed low values, although not consistently reduced over time of Al exposure. The relative expression of aquaporin genes belonging to PIP family (PIP1-1, PIP1-2 and PIP2) showed downregulation for ClPIP1-1 and ClPIP2 and upregulation for ClPIP1-2 in plants exposed to Al. Furthermore, ClPIP1-1 was positively correlated with A and gs in plants exposed to Al. Therefore, downregulation of ClPIP1-1 and ClPIP2 in roots of 'Rangpur' lime plants could be associated with the low leaf hydration of this species when exposed to Al.