ABA and chromatin remodelling regulate the activity-dormancy cycle in hybrid aspen

One of the most important survival strategies plants have evolved is the cessation of growth and development of dormancy in response to the seasonal changes. Apical meristems of deciduous woody plants living in temperate and boreal zones undergo a yearly cycle between an active and a dormant state, which allows them to protect the meristem and avoid damage provoked by extremes of low temperatures during the winter. The transition between an active and a dormant state includes a complex network of physiological and developmental processes such as acquisition of cold hardiness, bud formation and maturation and metabolic changes, which are underlined by a global change in gene expression. The studies described in my thesis provide an overview of the transcriptional control underlying the activity-dormancy cycle and are aimed to dissect the regulation of overlapping short days (SD)-induced processes. We investigated the control of SD-induced bud formation and maturation, acquisition of adaptive responses and of endodormancy and identified novel key molecular players regulating these processes. Our results provide evidence for a composite control of the activity-dormancy cycle by the SD signal that involves plant hormone abscisic acid (ABA) and a component of a chromatin remodelling complex, FERTILISATION INDEPEDENDENT ENDOSPERM (FIE), as key players. Importantly, our work reveals a degree of conservation in the regulatory framework for the control of dormancy in seeds and apical buds

A multi-omics approach reveals function of Secretory Carrier-Associated Membrane Proteins in wood formation of​ ​​Populus​​ ​trees

Background: Secretory Carrier-Associated Membrane Proteins (SCAMPs) are highly conserved 32–38 kDa proteins that are involved in membrane trafficking. A systems approach was taken to elucidate function of SCAMPs in wood formation of Populus trees. Phenotypic and multi-omics analyses were performed in woody tissues of transgenic Populus trees carrying an RNAi construct for Populus tremula x tremuloides SCAMP3 (PttSCAMP3;Potri.019G104000). Results: The woody tissues of the transgenic trees displayed increased amounts of both polysaccharides and lignin oligomers, indicating increased deposition of both the carbohydrate and lignin components of the secondary cell walls. This coincided with a tendency towards increased wood density as well as significantly increased thickness of the suberized cork in the transgenic lines. Multivariate OnPLS (orthogonal projections to latent structures) modeling of five different omics datasets (the transcriptome, proteome, GC-MS metabolome, LC-MS metabolome and pyrolysis-GC/MS metabolome) collected from the secondary xylem tissues of the stem revealed systemic variation in the different variables in the transgenic lines, including changes that correlated with the changes in the secondary cell wall composition. The OnPLS model also identified a rather large number of proteins that were more abundant in the transgenic lines than in the wild type. Several of these were related to secretion and/or endocytosis as well as both primary and secondary cell wall biosynthesis. Conclusions: Populus SCAMP proteins were shown to influence accumulation of secondary cell wall components, including polysaccharides and phenolic compounds, in the woody tissues of Populus tree stems. Our multi-omics analyses combined with the OnPLS modelling suggest that this function is mediated by changes in membrane trafficking to fine-tune the abundance of cell wall precursors and/or proteins involved in cell wall biosynthesis and transport. The data provides a multi-level source of information for future studies on the function of the SCAMP proteins in plant stem tissues.Bio4Energ

Additional file 5: of A multi-omics approach reveals function of Secretory Carrier-Associated Membrane Proteins in wood formation of​ ​​Populus​​ ​trees

LC-MS metabolomic analysis of wild type and PttSCAMP3 RNAi plants. (XLSX 64 kb

Additional file 3: of A multi-omics approach reveals function of Secretory Carrier-Associated Membrane Proteins in wood formation of​ ​​Populus​​ ​trees

RNAseq analysis of wild type and PttSCAMP3 RNAi plants. (XLSX 1841 kb

Photoperiod- and temperature-mediated control of phenology in trees – a molecular perspective

(Table presented.). Summary: Trees growing in boreal and temperate regions synchronize their growth with seasonal climatic changes in adaptive responses that are essential for their survival. These trees cease growth before the winter and establish a dormant state during which growth cessation is maintained by repression of responses to growth-promotive signals. Reactivation of growth in the spring follows the release from dormancy promoted by prolonged exposure to low temperature during the winter. The timing of the key events and regulation of the molecular programs associated with the key stages of the annual growth cycle are controlled by two main environmental cues: photoperiod and temperature. Recently, key components mediating photoperiodic control of growth cessation and bud set have been identified, and striking similarities have been observed in signaling pathways controlling growth cessation in trees and floral transition in Arabidopsis. Although less well understood, the regulation of bud dormancy and bud burst may involve cell–cell communication and chromatin remodeling. Here, we discuss current knowledge of the molecular-level regulation of the annual growth cycle of woody trees in temperate and boreal regions, and identify key questions that need to be addressed in the future

The peach HECATE3-like gene FLESHY plays a double role during fruit development.

Tight control of cell/tissue identity is essential for a correct and functional organ patterning, an important component of overall fruit development and eventual maturation and ripening. Despite many investigations regarding the molecular determinants of cell identity in fruits of different species, a useful model able to depict the regulatory networks governing this relevant part of fruit development is still missing. Here we described the peach fruit as a system to link the phenotype of a slow ripening (SR) selection to an altered transcriptional regulation of genes involved in determination of mesocarp cell identity providing insight toward molecular regulation of fruit tissue formation. Morpho-anatomical observations and metabolomics analyses performed during fruit development on the reference cultivar Fantasia, compared to SR, revealed that the mesocarp of SR maintained typical immaturity traits (e.g. small cell size, high amino acid contents and reduced sucrose) throughout development, along with a strong alteration of phenylpropanoid contents, resulting in accumulation of phenylalanine and lignin. These findings suggest that the SR mesocarp is phenotypically similar to a lignifying endocarp. To test this hypothesis, the expression of genes putatively involved in determination of drupe tissues identity was assessed. Among these, the peach HEC3-like gene FLESHY showed a strongly altered expression profile consistent with pit hardening and fruit ripening, generated at a post-transcriptional level. A double function for FLESHY in channelling the phenylpropanoid pathway to either lignin or flavour/aroma is suggested, along with its possible role in triggering auxin-ethylene cross talk at the start of ripening