Glutathione transferase, but not agglutinin, is a dormancy-related protein in Castanea crenata trees

Uncovering the complex regulatory network of spring bud sprouting in tea plants: insights from metabolic, hormonal, and oxidative stress pathways

The sprouting process of tea buds is an essential determinant of tea quality and taste, thus profoundly impacting the tea industry. Buds spring sprouting is also a crucial biological process adapting to external environment for tea plants and regulated by complex transcriptional and metabolic networks. This study aimed to investigate the molecular basis of bud sprouting in tea plants firstly based on the comparisons of metabolic and transcriptional profiles of buds at different developmental stages. Results notably highlighted several essential processes involved in bud sprouting regulation, including the interaction of plant hormones, glucose metabolism, and reactive oxygen species scavenging. Particularly prior to bud sprouting, the accumulation of soluble sugar reserves and moderate oxidative stress may have served as crucial components facilitating the transition from dormancy to active growth in buds. Following the onset of sprouting, zeatin served as the central component in a multifaceted regulatory mechanism of plant hormones that activates a range of growth-related factors, ultimately leading to the promotion of bud growth. This process was accompanied by significant carbohydrate consumption. Moreover, related key genes and metabolites were further verified during the entire overwintering bud development or sprouting processes. A schematic diagram involving the regulatory mechanism of bud sprouting was ultimately proposed, which provides fundamental insights into the complex interactions involved in tea buds.

Immunolocalization indicates plasmodesmal trafficking of storage proteins during cambial reactivation in Populus nigra

BACKGROUND AND AIMS

Cambium reactivation after dormancy and budbreak in deciduous trees requires a supply of mobilized reserve materials. The pathway and mode of transfer of these materials are poorly understood.

METHODS

Transport of reserve materials during cambium reactivation in Populus nigra was investigated by conventional and immunocytochemical TEM analyses, SDS-PAGE, western blotting and intracellular microinjection of fluorescent dyes.

KEY RESULTS

Proteinaceous compounds stored in vacuoles and protein bodies of vascular cells and ray cells disappeared within 3 weeks after cambial reactivation and budbreak. Some of these proteins (32 kDa, 30 kDa and 15 kDa) were labelled by lectin antibodies in SDS-PAGE. The same antibodies were localized to plasmodesmata (PDs) between phloem parenchyma, ray cells and fusiform cambial cells. In addition, proteinaceous particles were localized inside the cytoplasmic sleeves of these PDs during budbreak. During this period, the functional diameter of PDs was about 2.2 nm which corresponds approximately to the Stokes' radius of the detected 15-kDa protein.

CONCLUSIONS

Lectin-like reserve proteins or their degradation products seem to be transferred through PDs of phloem parenchyma and rays during cambial reactivation and budbreak. PD transfer of storage proteins is a novelty which supports the concept of symplasmic nutrient supply to the cambial region.

Japanese chestnut (Castanea crenata) agglutinin may have a role as vegetative storage protein

The expression of Japanese chestnut (Castanea crenata) agglutinin (CCA) and its mRNA was investigated in nitrogen-fertilized young potted plants and in floral organs of adult trees. Two levels of N were used: 10 and 20mM NH(4)NO(3). Both levels increased protein content in all vegetative organs, though the magnitude of the increase differed. The highest increase was observed in stems. High levels were retained in 20mM N-fertilized plants, whereas the protein content decreased at 10mM N fertilization. Expression of CCA and its mRNA was observed in young leaves and stems, and their quantities depended on the amount of N fertilizer supplied. In mature leaves, CCA was detected in the first 4 weeks, but its mRNA was undetectable throughout the experimental period. Neither CCA nor its mRNA was detected in roots. In floral organs, CCA and its mRNA were expressed throughout the flower but their quantities differed. These results suggest that CCA acts as a vegetative storage protein, which functions in temporary nitrogen reserve. The results also suggest that expression of CCA is regulated at both transcriptional and translational levels.