http://www.biologie.uni-freiburg.de/data/bio3/laux/publications_files/Mayer1998.pdf

Role of WUSCHEL in Regulating Stem Cell Fate in the Arabidopsis Shoot Meristem

Recent advances in the development of genome editing technologies based on programmable nucleases have substantially improved our ability to make precise changes in the genomes of eukaryotic cells. Genome editing is already broadening our ability to elucidate the contribution of genetics to disease by facilitating the creation of more accurate cellular and animal models of pathological processes. A particularly tantalizing application of programmable nucleases is the potential to directly correct genetic mutations in affected tissues and cells to treat diseases that are refractory to traditional therapies. Here we discuss current progress toward developing programmable nuclease–based therapies as well as future prospects and challenges.

Therapeutic genome editing: prospects and challenges

Abiotic stresses such as drought, high salinity, and cold are common adverse environmental conditions that significantly influence plant growth and productivity worldwide. The phytohormone abscisic acid (ABA) plays an important role in physiological and developmental responses as well as in co-ordinating various stress signal transduction pathways in plants. DREBs (dehydration responsive element binding) are important plant transcription factors (TFs) that regulate the expression of many stress-inducible genes mostly in an ABA-independent manner and play a critical role in improving the abiotic stress tolerance of plants by interacting with a DRE/CRT cis-element present in the promoter region of various abiotic stress-responsive genes. This review summarizes recent studies highlighting the role of the DRE-binding family of TFs in the adaptive responses to different abiotic stresses and their structural and functional characters with emphasis on the expression and regulation of DREBs. The practical and application value of DREBs in crop improvement, such as stress tolerance engineering as well as marker-assisted selection (MAS), has also been discussed.

/pdf/role-of-drebs-in-regulation-of-abiotic-stress-responses-in-1whj5367cl.pdf

Role of DREBs in regulation of abiotic stress responses in plants

Fruit morphogenesis is a process unique to flowering plants, and yet little is known about its developmental control. Following fertilization, fruits typically undergo a dramatic enlargement that is accompanied by differentiation of numerous distinct cell types. We have identified a mutation in Arabidopsis called fruitfull (ful-1), which abolishes elongation of the silique after fertilization. The ful-1 mutation is caused by the insertion of a DsE transposable enhancer trap element into the 5′ untranslated leader of the AGL8 MADS-box gene. βglucuronidase (GUS) reporter gene expression in the enhancer trap line is observed specifically in all cell layers of the valve tissue, but not in the replum, the septum or the seeds, and faithfully mimics RNA in situ hybridization data reported previously. The lack of coordinated growth of the fruit tissues leads to crowded seeds, a failure of dehiscence and, frequently, the premature rupture of the carpel valves. The primary defect of ful-1 fruits is within the valves, whose cells fail to elongate and differentiate. Stomata, which are frequent along the epidermis of wild-type valves, are completely eliminated in the ful mutant valves. In addition to the effect on fruit development, ful cauline leaves are broader than those of wild type and show a reduction in the number of internal cell layers. These data suggest that AGL8/FUL regulates the transcription of genes required for cellular differentiation during fruit and leaf development. SUMMARY

/pdf/the-fruitfull-mads-box-gene-mediates-cell-differentiation-16b4i2wimh.pdf

The FRUITFULL MADS-box gene mediates cell differentiation during Arabidopsis fruit development

http://genesdev.cshlp.org/content/11/10/1207.full.pdf

POU domain family values: flexibility, partnerships, and developmental codes.

Plant-specific transcription factors belonging to the dehydration response element binding (DREB)/C-repeat binding factor (CBF) subfamily of the AP2/EREBP family specifically interact with dehydration-responsive elements (DRE)/C-repeat (CRT) and control the expression of many stress-inducible genes in plants. Two major subgroups of DREB proteins are represented by DREB1 and DREB2, which are induced specifically under cold and drought/salt stress, respectively. A DREB2 transcription factor gene from sorghum, SbDREB2 was identified and cloned in binary vectors, such that it was driven either by a constitutive CaMV35S promoter or a stress-inducible rd29A promoter. These gene constructs were transferred into rice through Agrobacterium tumefaciens-mediated transformation. Expression patterns of the native DREB gene (OsDREB2) and the transgene (SbDREB2) were similar. Both genes showed induction at 1 h exposure to drought, after which expression gradually dropped to basal levels by 24 h. Constitutive expression of SbDREB2 led to pleiotropic effects in rice and these transgenics did not set seed. The rd29A: SbDREB2 rice plants set seed and the grains collected from primary transformants were sown to raise T1 plants. The drought-stressed rd29A: SbDREB2 transgenics showed a significantly higher number of panicles as compared to the wild-type rice plants. Other phenological and agronomic traits were not affected in wild-type and rd29A: SbDREB2 transgenic rice.

Transgenic expression of sorghum DREB2 in rice improves tolerance and yield under water limitation

The maize homebox gene knotted1 (kn1) is expressed in vegetative and floral meristems and is down-regulated at the site of primordia formation. kn1-related genes from maize and other species also show meristem-specific expression and offer additional tools for studying the activities of shoot meristems. Members of this gene family are expressed early in embryogenesis, providing molecular markers for meristem initiation. Ectopic expression of either kn1 or a related Arabidopsis gene, KNAT1, causes dramatic alterations in Arabidopsis and tobacco leaf morphology. Most significantly, meristems form on the leaf, producing small shoots. We discuss whether the phenotypes can be interpreted as changes in positional information or timing of determination.

Homeobox genes in the functioning of plant meristems.

Bacterial blight (BB), a major disease of rice, is caused by Xanthomonas oryzae pv. oryzae (Xoo). Six distinct Indian isolates of Xanthomonas oryzae were tested on rice genetic backgrounds carrying single or multiple BB resistance genes. Three BB resistance genes were introduced into a susceptible line, MH2R, by marker assisted selection, which resulted in a gain of resi stance. In add ition, Pusa Basmati 1 (PB1) transgenic lines carrying the BB resistance gene, Xa21, and IR72Xa21 transgenic lines were evaluated after inocul ation with the six Xoo isolates. It was found that PB1 lines expressing the Xa21 gene were susceptible to the six Xoo isolates. These results indicate that introducing mult iple BB resistance genes by marker -assisted selection may be a more effective strategy in breeding for BB resi stance against Indian isolates.

Evaluation of bacterial blight resistance in rice lines carrying multiple resistance genes and Xa21 transgenic lines

The large body of information that has come from genome sequencing projects has demonstrated that plants and animals have many sequences in common, suggesting that they have either co-opted the same molecules for different purposes, or that they utilize similar mechanisms (Reuzeau and Pont-Lezica 1995; Clark 1996). One might expect many housekeeping tasks, such as regulation of the cell cycle, to be similar in plants and animals, but what of the multicellular tasks, the developmental processes that coordinate growth and differentiation of cells? Unlike animal cells, plant cells never move, thus induction by cell movement such as occurs during gastrulation in animal embryo development, is not likely to occur. Lineage-based development would be convenient in plants as they are forever attached to their parent cell; however, with few exceptions (Sachs 1978), plant cells do not appear to differentiate based on lineage. How, then do plant cells find their cues? A growing body of clonal analysis supports the statement that plant cells differentiate according to position (Steffensen 1968; Johri and Coe 1983; Jegla and Sussex 1989; Irish and Sussex 1992; Bossinger and Smyth 1996). Initial cells are as likely to contribute to somatic tissues such as leaves as they are to the eggs and sperm embedded in the flower; in other words, there are no sequestered germ cells. The cells of the epidermis, or outer layer, are clonally related, but if a cell divides such that a daughter cell is pushed into the internal tissues, that daughter cell takes on the fates of internal cells. Similarly, the internal cells that find themselves pushed into the epidermis differentiate as epidermis (Stewart 1978). Differentiation of cell types in the Arabidopsis root appears to follow specific lineages (Dolan et al. 1993, 1994; Scheres et al. 1994), however, laser ablation experiments have shown that ablated cells are replaced by cells from another lineage which differentiate according to their new position (van den Berg 1995). These experiments suggest that the apparent lineage of the root is a consequence of the simple and regular cellular arrangements. Positional information has also been shown to play a role in the differentiation of photosynthetic cell types in

/pdf/cell-cell-interactions-during-plant-development-ann4fo8liw.pdf

Cell-cell interactions during plant development.

SpOct, a Gene Encoding the Major Octamer-Binding Protein in Sea Urchin Embryos: Expression Profile, Evolutionary Relationships, and DNA Binding of Expressed Protein

Bharat Char

Papers

Transgenic expression of sorghum DREB2 in rice improves tolerance and yield under water limitation

Homeobox genes in the functioning of plant meristems.

Evaluation of bacterial blight resistance in rice lines carrying multiple resistance genes and Xa21 transgenic lines

Cell-cell interactions during plant development.

SpOct, a Gene Encoding the Major Octamer-Binding Protein in Sea Urchin Embryos: Expression Profile, Evolutionary Relationships, and DNA Binding of Expressed Protein