The Ca2+ -dependent DNases are involved in secondary xylem development in Eucommia ulmoides.

Secondary xylem development has long been recognized as a typical case of programmed cell death (PCD) in plants. During PCD, the degradation of genomic DNA is catalyzed by endonucleases. However, to date, no endonuclease has been shown to participate in secondary xylem development.

The proteasome is responsible for caspase-3-like activity during xylem development.

Xylem development is a process of xylem cell terminal differentiation that includes initial cell division, cell expansion, secondary cell wall formation and programmed cell death (PCD). PCD in plants and apoptosis in animals share many common characteristics. Caspase-3, which displays Asp-Glu-Val-Asp (DEVD) specificity, is a crucial executioner during animal cells apoptosis.

Molecular features of secondary vascular tissue regeneration after bark girdling in Populus.

Regeneration is a common strategy for plants to repair damage to their tissue after attacks from other organisms or physical assaults. However, how differentiating cells acquire regenerative competence and rebuild the pattern of new tissues remains largely unknown. Using anatomical observation and microarray analysis, we investigated the morphological process and molecular features of secondary vascular tissue regeneration after bark girdling in trees.

Regulation of cell cycle regulators by environmental signals during growth-dormancy cycle of trees.

Climate change such as changing temperature and increasing concentrations of atmospheric CO(2), are likely to drive significant modifications in forests. While many studies have demonstrated the responses and adoptions of tree to fluctuations in climatic and environmental conditions, the impact of environmental signals on trees is complex and poorly understood with respect to the molecular biology in context of the seasonal change of environmental signals. This addendum is focused on the impact of environmental signals on growth-dormancy cycle of trees growing in temperate regions, especially the regulation of cell cycle regulators by temperature and photoperiod.

Induction of PtoCDKB and PtoCYCB transcription by temperature during cambium reactivation in Populus tomentosa Carr.

Cell cycle progression requires interaction between cyclin-dependent kinase B (CDKB) and cyclin B (CYCB). The seasonal expression patterns of the CDKB and CYCB homologues from Populus tomentosa Carr. were investigated, and effects of temperature and exogenous indole-3-acetic acid (IAA) on their expression were further studied in water culture experiments.

Occurrence of the transition of apical architecture and expression patterns of related genes during conversion of apical meristem identity in G2 pea.

G2 pea exhibits an apical senescence delaying phenotype under short-day (SD) conditions; however, the structural basis for its apical development is still largely unknown. In the present study, the apical meristem of SD-grown G2 pea plants underwent a transition from vegetative to indeterminate inflorescence meristem, but the apical meristem of long-day (LD)-grown G2 pea plants would be further converted to determinate floral meristem. Both SD signal and GA(3) treatment enhanced expression of the putative calcium transporter PPF1, and pea homologs of TFL1 (LF and DET), whereas LD signal suppressed their expression at 60 d post-flowering compared with those at 40 d post-flowering.

PPF1 may suppress plant senescence via activating TFL1 in transgenic Arabidopsis plants.

Senescence, a sequence of biochemical and physiological events, constitutes the final stage of development in higher plants and is modulated by a variety of environmental factors and internal factors. PPF1 possesses an important biological function in plant development by controlling the Ca2+ storage capacity within chloroplasts. Here we show that the expression of PPF1 might play a pivotal role in negatively regulating plant senescence as revealed by the regulation of overexpression and suppression of PPF1 on plant development.

Phloem transdifferentiation from immature xylem cells during bark regeneration after girdling in Eucommia ulmoides Oliv.

Eucommia ulmoides Oliv. (Eucommiaceae), a traditional Chinese medicinal plant, was used to study phloem cell differentiation during bark regeneration after girdling on a large scale. Here it is shown that new sieve elements (SEs) appeared in the regenerated tissues before the formation of wound cambium during bark regeneration after girdling, and they could originate from the transdifferentiation of immature/differentiating axial xylem cells left on the trunk.

Formation of archegonium chamber is associated with nucellar-cell programmed cell death in Ginkgo biloba.

The archegonium chamber in Ginkgo biloba L. is a pathway for spermatozoids swimming towards the archegonium for fertilization. The objective of this study was to elucidate the mechanism of archegonium chamber formation.

ABP1 expression regulated by IAA and ABA is associated with the cambium periodicity in Eucommia ulmoides Oliv.

A cDNA clone of Eucommia ulmoides Oliv. encoding auxin binding protein 1 (ABP1), one of the putative receptors of auxin, was isolated, and the seasonal expression of ABP1 in relation to IAA and ABA annual variation was investigated by different technical approaches including RT-PCR, real-time PCR, northern blotting, western blotting, and immunolocalization. In the cambial region, ABP1 expression at both the protein and the mRNA level was found to be high, low, and remarkably scarce in the active, quiescent, and resting stages, respectively, during cambium periodicity.

Regeneration of the secondary vascular system in poplar as a novel system to investigate gene expression by a proteomic approach.

Wood formation is a complex process composing many biological events. To access its key developmental stages, we have established a regeneration system that can mimic the initiation and differentiation of cambium cells for Chinese white poplar. Anatomical studies showed that new cambium and xylem re-appeared in sequence within a few weeks after being debarked.

Opposite patterns in the annual distribution and time-course of endogenous abscisic acid and indole-3-acetic acid in relation to the periodicity of cambial activity in Eucommia ulmoides Oliv.

The seasonal change of free abscisic acid (ABA) and indole-3-acetic acid (IAA) and their relationship with the cambial activity in Eucommia ulmoides trees were investigated by ABA and IAA immunolocalization using primary polyclonal and rhodamine-red fluorescing secondary antibodies, ABA and IAA quantification using high performance liquid chromatography (HPLC), and systematic monitoring of vascular cell layers production. ABA and IAA clearly displayed opposite annual distribution patterns. In the active period (AP), both immunolocalization and HPLC detected an abrupt decrease of ABA, reaching its lowest level in the summer.

PPF1 inhibits programmed cell death in apical meristems of both G2 pea and transgenic Arabidopsis plants possibly by delaying cytosolic Ca2+ elevation.

PPF1 encodes a putative calcium ion carrier that affects the flowering time of transgenic Arabidopsis by modulating Ca(2+) storage capacities in chloroplasts of a plant cell. In the current work, we found that differential expression of PPF1 might affect processes of programmed cell death (PCD) since DNA fragmentation was detected in senescencing apical buds of long day-grown G2 pea (Pisum sativum L.) plants, but was not in non-senescencing short day-grown counterparts at all growth stages.

Relationship between endogenous indole-3-acetic acid and abscisic acid changes and bark recovery in Eucommia ulmoides Oliv. after girdling.

Eucommia ulmoides (Eucommiaceae), a traditional Chinese medicinal plant, is often subjected to severe manual peeling of its bark. If the girdled trunk is well protected from desiccation, new bark forms within 1 month. It has been proposed that phytohormones play a key role in this process.

Toward understanding the different function of two types of parenchyma cells in bamboo culms.

The bamboo, woody monocot, has two types of parenchyma cells in the ground tissues of its culm, in contrast to a single type of parenchyma cell in rice, maize and other major crop species. The distribution of cell wall components, including lignin, (1-->3), (1-->4)-beta-D-glucans (MGs), the highly-substituted glucuronoarabinoxylans (hsGAXs) and low-branched xylans (lbXs) in ground parenchyma tissue of Phyllostachys heterocycla var. pubescens culms was studied at various developmental stages using light microscopy (LM), UV-microscopy, transmission electron microscopy (TEM) and immunolabeling techniques.