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ABSTRACT: The ASYMMETRIC LEAVES2-LIKE/LATERAL ORGAN BOUNDARIES (LOB) DOMAIN (ASL/LBD) genes encode plant-specific nuclear proteins containing the conserved domain AS2/LOB. In this study, the function of a member of the Arabidopsis thaliana AS2/LOB gene family, ASL11/LBD15, was investigated. The results show that ASL11/LBD15 is expressed in the meristems of shoot apex, root apex, organ boundaries, and developing seeds. Overexpression of ASL11/LBD15 resulted in aberrant arrangements in the tunica cell layers of the shoot apical meristem (SAM). Two-week-old transgenic plants developed needle-like leaves in addition to regular leaves, while 6-week-old transformants displayed clustered cauline leaves suggesting altered SAM development. qRT-PCR analysis revealed that the WUSCHEL (WUS) transcript level was strongly up-regulated in plants overexpressing ASL11/LBD15 compared with the wild-type plants. Furthermore, inducible ASL11/LBD15 ectopic expression activated ectopic expression of WUS and affected the differentiation of leaf epidermal cells. Therefore, our results suggest that ASL11/LBD15 affects cellular differentiation in the SAM and regulates WUS expression.
Planta 02/2013; · 3.00 Impact Factor
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ABSTRACT: In Arabidopsis, two AUXIN RESPONSE FACTORs (ARF7 and ARF19) and several Aux/IAAs regulate auxin-induced lateral root (LR) formation. As direct targets of ARF7 and ARF19, LATERAL ORGAN BOUNDARIES DOMAIN 16 (LBD16), LBD29, and LBD18 have a biological function in the formation of lateral roots (LRs). However, the details of the functions of these three LBDs have remained unclear. Each single T-DNA insert mutant has been shown to have slightly fewer LRs than the wild type. We then created a triple mutant, which exhibited a dramatic defect in the LR formation. Our results show that the lbd mutations can lead to impairment in auxin-induced pericycle cell division and in the expression levels of some D-type cyclins (CYCDs). Simultaneously, PLETHORA (PLT) and PIN-FORMED (PIN), which have been well documented to promote cell mitotic activity and are required for auxin response effects, were down-regulated by these lbd mutations. Our results so far indicate that CYCDs, PLT, and PINs are the main targets of the LBDs. We believe that these three LBDs are involved in cell cycle progression of the pericycle in response to auxin. Overexpression of any of these three LBD genes in the triple mutant was found incapable of completely replacing the other two LBDs. The phenotypes of lbd29 mutants were not completely consistent with lbd16 or lbd18 mutants. This indicates that LBD29 may play a distinctive role compared with LBD16 or LBD18 and LBDs might play partially independent roles during the formation of LRs.
Planta 06/2012; 236(4):1227-37. · 3.00 Impact Factor
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ABSTRACT: Dedifferentiation is an important cellular process in plant development. Successful in vitro culture of plant tissues for
micropropagation and transgenic plant development depend on dedifferentiation and redifferentiation of explants. However,
the molecular basis of dedifferentiation is not well understood. To elucidate the dedifferentiation mechanism, microarray
analysis was carried out to study the transcriptome changes associated with dedifferentiation in the petiole of Arabidopsis thaliana. Analysis of global gene expression profiles allowed us to identify key developmental genes that showed differential expression
during the dedifferentiation process. LBD29 was selected as one of the candidate genes that regulate the process of lateral root initiation in Arabidopsis
thaliana. The role of the LBD29/ASL16 gene in effecting dedifferentiation of pericycle cells and lateral root formation is discussed.
Keywords
Arabidopsis thaliana
-Dedifferentiation-
LBD29
-Pericycle cells
Plant Growth Regulation 04/2012; 62(2):127-136. · 1.60 Impact Factor
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ABSTRACT: LATERAL ORGAN BOUNDARIES DOMAIN 29 (LBD29), an important molecule downstream of auxin response factors ARF7 and ARF19, has a critical role in lateral root formation in Arabidopsis thaliana. The cell cycle activation of pericycle cells and their specification triggered by auxin are crucial for the initiation of lateral roots. In this study, we attempted to determine whether LBD29 is involved in auxin signalling and/or cell cycle regulation and to characterize the roles of LBD29 in these processes.
The impact of LBD29 on cell cycling progression in pericycle cells was investigated in lbd29 loss-of-function mutant or LBD29-over-expressing plants. The cell cycle was determined by measuring the expression of some cell cycle-related genes using in situ hybridization and quantitative real-time reverse transcription-PCR (qRT-PCR). Furthermore, the cell division in the root explants from either the lbd29 mutant, LBD29-over-expressing plants or the wild type grown in auxin-rich media was also analysed and compared by the distribution of DR5:β-glucuronidase (GUS) in the primordia or by the expression of PIN-FORMED (PIN) members and PLETHROA 1 (PLT1) which represented the auxin response by the pericycle cells.
lbd29 mutation resulted in reduced numbers of lateral roots and primordia, whereas LBD29 over-expression resulted in more lateral root and primordia formation than in the wild type. More importantly, the level of LBD29 expression was found to be positively correlated with the level of expression of cell cycle-related genes and correlated with the numbers of subcellular organelles found in pericycle cells in the maturation zone. In addition, an in vitro experiment using root explants demonstrated that the presence of LBD29 was required for the maintenance of the cell division capacity of the pericycle. Furthermore, LBD29 appeared to modify PIN-dependent auxin signalling in the primordia since there was a correlated association between the expression of PINs, PLT1 and DR5:GUS and the expression of LBD29.
The ability of LBD29 to regulate lateral root initiation is associated with its maintenance of the cell division capacity of the pericycle in response to auxin and its involvement in the auxin signalling pathway.
Annals of Botany 02/2012; 110(1):1-10. · 4.03 Impact Factor
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ABSTRACT: Although the method of tissue culturing has been used widely in practice for a long time, and there are numerous hypotheses to explain the dedifferentiation phenomenon in the tissue culturing, many details of mechanism of dedifferentiation remain unclear. In the study, dedifferentiation process is initiated in the residual procambium, followed by the procambium-derived cells and finally xylem parenchyma cells under the culturing of Arabidopsis thaliana petiole explants. The procambium may induce its derivative cells to undergo dedifferentiation, which in turn induce the xylem parenchyma cells to dedifferentiate. This phenomenon is very similar to the activity of interfascicular cambium induced by intrafascicular cambium in secondary growth of plant stems. In the present study, only the paired procambium-derived cells and xylem parenchyma truly underwent dedifferentiation, whereas the initial changes in the procambium simply recovered the inherent meristematic capacity of those cells. In transverse section of petiole of A. thaliana, parenchyma cells outside the vascular bundle did not participate in dedifferentiation and gradually disintegrated under the culture conditions. Obviously, the time for initiation and difficulty underlain for undergoing dedifferentiation are dependent on the differential degree and location of parenchyma cells in the petiole.
Protoplasma 05/2010; 241(1-4):75-81. · 1.92 Impact Factor
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ABSTRACT: Differently colored quantum dot (QD) nanoparticles are incorporated into bovine serum albumin (BSA) nanospheres by spray-drying followed by thermal denaturization, which is a rapid, highly efficient, large scale, and low cost method. Because the spray-dryer is equipped with an ultrasonic atomizer, most of the nanospheres are no more than 550 nm in diameter and a have narrow size distribution. Ultrathin sections (70 nm) of nanospheres are first prepared using a technique which is normally applied to cell sectioning. The section images show that the QD-BSA nanospheres are solid, and that the QDs are successfully dispersed inside the BSA nanospheres. The nanospheres emit bright fluorescence, and their fluorescence stabilities are not obviously changed compared with that of the QDs. This work provides a novel and simple method for preparing nanoscale spheres encapsulating differently colored QDs. We also present an ultrathin sectioning method for investigating the interior details of nanomaterials.
Nanoscale 04/2010; 2(4):542-7. · 5.91 Impact Factor
