Histochemical Study of Enzyme Activity in the Shoot Apical Meristem of Brassica campestris L. during Transition to Flowering. I. Succinic Dehydrogenase

The Rauwolfia apical meristem has three zones which are cytologically recognizable, viz. tunica, corpus, and pith-cell meristem. Histochemically, however, these zonations are not discernible. The entire meristem either reacts positively or negatively for a particular enzyme. The apical meristem and procambial strands give a strong positive reaction for cytochrome oxidase, succinic dehydrogenase, and total protein. The pith cells react positively with peroxidase, acid phosphatase, and phosphorylase. Alkaline phosphatase is distributed throughout the meristematic and non-meristematic areas of the shoot apex. Cells in these areas appear to give slight reaction for glucose-6-phosphatase and 5-nucleotidase. Activities of several enzyme systems, such as cytochrome oxidase, peroxidase, succinic dehydrogenase, and acid phosphatase, were localized in the sclereid initials. Commonly the sclereids give more intensified enzymatic reaction than the pith parenchyma cells.

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Effects of FLOWERING LOCUS T on FD during the transition to flowering at the shoot apical meristem of Arabidopsis thaliana

10.1101/483925 ◽

2018 ◽

Author(s):

Silvio Collani ◽

Manuela Neumann ◽

Levi Yant ◽

Markus Schmid

Keyword(s):

Shoot Apical Meristem ◽

Apical Meristem ◽

Protein Complexes ◽

Shoot Meristem ◽

Bzip Transcription Factor ◽

Flowering Locus T ◽

Wide Scale ◽

Flowering Locus ◽

Plant Life Cycle ◽

Transition To Flowering

ABSTRACTThe transition to flowering is a crucial step in the plant life cycle that is controlled by multiple endogenous and environmental cues, including hormones, sugars, temperature, and photoperiod. Permissive photoperiod induces FLOWERING LOCUS T (FT) in the phloem companion cells of leaves. The FT protein then acts as a florigen that is transported to the shoot apical meristem (SAM) where it physically interacts with the bZIP transcription factor FD and 14-3-3 proteins. However, despite the importance of FD for promoting flowering, its direct transcriptional targets are largely unknown. Here we combined ChIP-seq and RNA-seq to identify targets of FD at the genome-wide scale and assess the contribution of FT to binding DNA. We further investigated the ability of FD to form protein complexes with FT and TFL1 through the interaction with 14-3-3 proteins. Importantly, we observe direct binding of FD to targets involved in several aspects of the plant development not directly related to the regulation of flowering time. Our results confirm FD as central regulator of the floral transition at the shoot meristem and provides evidence for crosstalk between the regulation of flowering and other signaling pathways.Material DistributionThe author responsible for distribution of materials integral to the findings presented in this article in accordance with the policy described in the Instructions for Authors (www.cell.com/molecular-plant/authors): Markus Schmid ([email protected]).Contact InformationUmeå Plant Science Centre (UPSC), Dept. of Plant Physiology Umeå University, SE-901 87 Umeå, SWEDEN

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Descriptive and Quantitative Study of Ultrastructural Changes in the Apical Meristem of Mustard in Transition to Flowering

Journal of Cell Science ◽

10.1242/jcs.16.2.421 ◽

1974 ◽

Vol 16 (2) ◽

pp. 421-432

Author(s):

A. HAVELANGE ◽

G. BERNIER ◽

A. JACQMARD

Keyword(s):

Apical Meristem ◽

Quantitative Methods ◽

Succinic Dehydrogenase ◽

Ultrastructural Changes ◽

Cytoplasmic Matrix ◽

Membrane Area ◽

Early Effect ◽

Long Day ◽

Transition To Flowering ◽

In Cells

Transition to flowering was induced in the shoot apical meristem of Sinapis alba (mustard), a long-day species, by subjecting vegetative plants to a single 22-h long day. The ultrastructural changes occurring in the meristematic cells during the complete morphogenetic switch were investigated by quantitative methods. The earliest detectable changes are seen 18 h after the start of the inductive long day. One of these changes is the replacement of the large vacuoles of the cells of vegetative meristems by an increased number of smaller vacuoles in the cells of meristems of plants induced to flower (evoked meristems). The other earliest change is an increase in size of the chondriome. Remarkably enough both changes have in common that they lead to an increase in membrane area and are thus concerned with increased membrane synthesis. In this respect this very early effect of the leaf-generated floral stimulus is very similar to that produced by various animal and plant hormones in their respective target tissues. The large rise in chondriome size is paralleled by an increase in succinic dehydrogenase activity. Both changes certainly reflect a rise in cellular respiratory activity which produces the necessary energy supply for the morphogenetic switch. As the size of the plastidome does not change during the transition to flowering, the plastidome:chondriome ratio decreases markedly. The size of the cytoplasmic matrix is greater in cells of evoked meristems than in cells of vegetative meristems. A first size maximum is reached at 26 h after the start of the long day and a second at 54 h. These 2 maxima occur just prior to 2 mitotic waves culminating respectively at 26-30 and 62 h. The increases in amount of endoplasmic reticulum (ER) and dictyosome number that are found in evoked meristems collected just prior to or at the time of the second mitotic wave are also probably related to the mitotic activation of the tissue. As the size of the vacuolar apparatus considered as a whole does not change at all and the size of the cytoplasmic matrix increases, the vacuoles:cytoplasm ratio decreases in evoked meristems collected following 26 h after the start of the long day. Also, there is an unexpected decrease in the nucleus:cytoplasm ratio in the cells of evoked meristems after 46 h.

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