Chitinase, beta-1,3-glucanase, osmotin, and extensin are expressed in tobacco explants during flower formation.

Sequence analysis of five gene families that were isolated from tobacco thin cell layer explants initiating floral development [Meeks-Wagner et al. (1989). Plant Cell 1, 25-35] showed that two encode the pathogenesis-related proteins basic chitinase and basic beta-1,3-glucanase, while a third encodes the cell wall protein extensin, which also accumulates during pathogen attack. Another sequence family encodes the water stress-induced protein osmotin [Singh et al. (1989). Plant Physiol. 90, 1096-1101]. We found that osmotin was also induced by viral infection and wounding and, hence, could be considered a pathogenesis-related protein. These genes, which were highly expressed in explants during de novo flower formation but not in explants forming vegetative shoots [Meeks-Wagner et al. (1989). Plant Cell 1, 25-35], were also regulated developmentally in day-neutral and photoresponsive tobacco plants with high expression levels in the roots and moderate- to low-level expression in other plant organs including flowers. An unidentified gene family, FB7-4, had its highest level of expression in the basal internodes. Our findings indicate that these genes, some of which are conventionally considered to encode pathogen-related proteins, also have a complex association with normal developmental processes, including the floral response, in healthy plants.     

Cloning and Analysis of CFL-A LFY-like Gene from Cucumber

LFY and LFY-like genes have been shown to control the initiation of floral meristems in higher plants. The homologous eDNA of LFY, CFL, were cloned from cucumber ( Cucumis sativus L. ). Southern blot analysis showed it was a single copy gene in the cucumber genome. Northern blot analysis showed that it expressed in the floral buds and young leaves. The possible role of CFL in the floral and vegetative development of cucumber plant was discussed.     

黄瓜中LFY同源基因CFL的克隆和分析

ＬＦＹ同源基因在高等植物花分生组织的发生中发挥着重要的作用。克隆了黄瓜（ Ｃｕｃｕｍｉｓｓａｔｉｖｕｓ Ｌ．） 中的ＬＦＹ同源基因ＣＦＬ,Ｓｏｕｔｈｅｒｎ 杂交的结果显示它在黄瓜基因组中为单拷贝基因,Ｎｏｒｔｈｅｒｎ 杂交结果显示它主要在花芽和幼叶中表达。讨论了ＣＦＬ基因在黄瓜开花和营养生长中可能发挥的作用     

Expression of HtKNOT1, a class I KNOX gene, overlaps cell layers and development compartments of differentiating cells in stems and flowers of Helianthus tuberosus

In plant, post-embryonic development relies on the activities of indeterminate cell populations termed meristems, spatially clustered cell lineages, wherein a subset divides indeterminately. For correct growth, the plant must maintain a constant flow of cells through the meristem, where the input of dividing pluripotent cells offsets the output of differentiating cells. KNOTTED1-like homeobox (KNOX) genes are expressed in specific patterns in the plant meristems and play important roles in maintaining meristematic cell identity. We have analyzed the expression pattern of HtKNOT1, a class I KNOX gene of Helianthus tuberosus, in stems, inflorescence meristems, floral meristems and floral organs. HtKNOT1 is expressed in cambial cells, phloem cells and xylematic parenchyma within apical stem internodes, while in basal internodes HtKNOT1 expression was restricted to the presumptive initials and recently derived phloem cells. In the reproductive phase, HtKNOT1 mRNAs were detected in both the inflorescence and floral meristems as well within lateral organ primordia (i.e. floral bracts, petals, stamens and carpels). In more differentiated flowers, the expression of HtKNOT1 was restricted to developing ovules and pollen mother cells. HtKNOT1 may play a dual role being required to maintain the meristem initials as well as initiating differentiation and/or conferring new cell identity. In particular, it is possible that HtKNOT1 cooperates at floral level with additional factors that more specifically control floral organs and pollen development in H. tuberosus.     

Genomic approach to study floral development genes in Rosa sp

Cultivated for centuries, the varieties of rose have been selected based on a number of flower traits. Understanding the genetic and molecular basis that contributes to these traits will impact on future improvements for this economically important ornamental plant. In this study, we used scanning electron microscopy and sections of meristems and flowers to establish a precise morphological calendar from early rose flower development stages to senescing flowers. Global gene expression was investigated from floral meristem initiation up to flower senescence in three rose genotypes exhibiting contrasted floral traits including continuous versus once flowering and simple versus double flower architecture, using a newly developed Affymetrix microarray (Rosa1_Affyarray) tool containing sequences representing 4765 unigenes expressed during flower development. Data analyses permitted the identification of genes associated with floral transition, floral organs initiation up to flower senescence. Quantitative real time PCR analyses validated the mRNA accumulation changes observed in microarray hybridizations for a selection of 24 genes expressed at either high or low levels. Our data describe the early flower development stages in Rosa sp, the production of a rose microarray and demonstrate its usefulness and reliability to study gene expression during extensive development phases, from the vegetative meristem to the senescent flower.     

A petunia MADS box gene involved in the transition from vegetative to reproductive development.

We have identified a novel petunia MADS box gene, PETUNIA FLOWERING GENE (PFG), which is involved in the transition from vegetative to reproductive development. PFG is expressed in the entire plant except stamens, roots and seedlings. Highest expression levels of PFG are found in vegetative and inflorescence meristems. Inhibition of PFG expression in transgenic plants, using a cosuppression strategy, resulted in a unique nonflowering phenotype. Homozygous pfg cosuppression plants are blocked in the formation of inflorescences and maintain vegetative growth. In these mutants, the expression of both PFG and the MADS box gene FLORAL BINDING PROTEIN26 (FBP26), the putative petunia homolog of SQUAMOSA from Antirrhinum, are down-regulated. In hemizygous pfg cosuppression plants initially a few flowers are formed, after which the meristem reverts to the vegetative phase. This reverted phenotype suggests that PFG, besides being required for floral transition, is also required to maintain the reproductive identity after this transition. The position of PFG in the hierarchy of genes controlling floral meristem development was investigated using a double mutant of the floral meristem identity mutant aberrant leaf and flower (alf) and the pfg cosuppression mutant. This analysis revealed that the pfg cosuppression phenotype is epistatic to the alf mutant phenotype, indicating that PFG acts early in the transition to flowering. These results suggest that the petunia MADS box gene, PFG, functions as an inflorescence meristem identity gene required for the transition of the vegetative shoot apex to the reproductive phase and the maintenance of reproductive identity.     

Expression of CENTRORADIALIS (CEN) and CEN-like genes in tobacco reveals a conserved mechanism controlling phase change in diverse species.

Plant species exhibit two primary forms of flowering architecture, namely, indeterminate and determinate. Antirrhinum is an indeterminate species in which shoots grow indefinitely and only generate flowers from their periphery. Tobacco is a determinate species in which shoot meristems terminate by converting to a flower. We show that tobacco is responsive to the CENTRORADIALIS (CEN) gene, which is required for indeterminate growth of the shoot meristem in Antirrhinum. Tobacco plants overexpressing CEN have an extended vegetative phase, delaying the switch to flowering. Therefore, CEN defines a conserved system controlling shoot meristem identity and plant architecture in diverse species. To understand the underlying basis for differences between determinate and indeterminate architectures, we isolated CEN-like genes from tobacco (CET genes). In tobacco, the CET genes most similar to CEN are not expressed in the main shoot meristem; their expression is restricted to vegetative axillary meristems. As vegetative meristems develop into flowering shoots, CET genes are downregulated as floral meristem identity genes are upregulated. Our results suggest a general model for tobacco, Antirrhinum, and Arabidopsis, whereby the complementary expression patterns of CEN-like genes and floral meristem identity genes underlie different plant architectures.     

茎顶端分生组织在植物发育过程中的保持、转变和逆转

顶端分生组织(shoot apical meristems,SAM)为产生新的器官和组织而不断提供新的细胞,它的活性依赖于平衡分生组织细胞的增殖和器官发生之间关系的调控基因.来自不具备光合能力的顶端分生组织的细胞可形成具有光合能力的营养器官.在从营养生长到生殖发育的转变过程中,茎顶端分生组织,转变为花序分生组织,最终形成花分生组织.在进入开花决定状态以前,SAM的状态很大程度上受到环境信号和转录调控因子的影响.以模式植物拟南芥为主,对在顶端分生组织的保持和转变中复杂同时又有差异的基因调控网络进行讨论.在花和花序分生组织逆转过程中,SAM中的细胞也受到相关基因的调控,且表达方式存在明显的时空差异.因此,具有决定性的和未决定性双重特性的分生组织之间的转变和相互协调,对于器官发生和形态建成起到至关重要的作用.