조형택 교수

Expansins are cell-wall-loosening proteins that induce stress relaxation and extension of plant cell walls. To evaluate their hypothesized role in cell growth, we genetically manipulated expansin gene expression in Arabidopsis thaliana and assessed the consequent changes in growth and cell-wall properties. Various combinations of promoters were used to drive antisense and sense sequences of AtEXP10, which is maximally expressed in the growing leaf and at the base of the pedicel. Compared with co

The expression of two Arabidopsis expansin genes (AtEXP7 and AtEXP18) is tightly linked to root hair initiation; thus, the regulation of these genes was studied to elucidate how developmental, hormonal, and environmental factors orchestrate root hair formation. Exogenous ethylene and auxin, as well as separation of the root from the medium, stimulated root hair formation and the expression of these expansin genes. The effects of exogenous auxin and root separation on root hair formation required

Expansins are a family of proteins that catalyze long-term extension of isolated cell walls. Previously, two expansin proteins have been isolated from internodes of deepwater rice, and three rice expansin genes, Os-EXP1, Os-EXP2, and Os-EXP3, have been identified. We report here on the identification of a fourth rice expansin gene, Os-EXP4, and on the expression pattern of the rice expansin gene family in deepwater rice. Rice expansin genes show organ-specific differential expression in the cole

Plant ATP-binding cassette (ABC) transporters consist of largest family members among many other membrane transporters and have been implicated in various functions such as detoxification, disease resistance and transport of diverse substrates. Of the ABC-B/multi-drug resistance/P-glycoprotein (ABCB/MDR/PGP) subfamily, at least five members have been reported to mediate cellular transport of auxin or auxin derivatives. Although single mutant phenotypes of these genes are milder than PIN-FORMED (

Vascular plants develop distinctive root hair distribution patterns in the root epidermis, depending on the taxon. The three patterns, random (Type 1), asymmetrical cell division (Type 2), and positionally cued (Type 3), are controlled by different upstream fate-determining factors that mediate expression of root hair cell-specific genes for hair morphogenesis. Here, we address whether these root hair genes possess a common transcriptional regulatory module (cis-element) determining cell-type sp

Cell walls of deepwater rice (Oryza sativa L.) internodes undergo long-term extension (creep) when placed under tension in acidic buffers. This is indicative of the action of the cell wall-loosening protein expansin. Wall extension had a pH optimum of around 4.0 and was abolished by boiling. Acid-induced extension of boiled cell walls could be reconstituted by addition of salt-extracted rice or cucumber cell wall proteins. Cucumber expansin antibody recognized a single protein band of 24.5-kD ap

The root hair development is controlled by diverse factors such as fate-determining developmental cues, auxin-related environmental factors, and hormones. In particular, the soil environmental factors are important as they maximize their absorption by modulating root hair development. These environmental factors affect the root hair developmental process by making use of diverse hormones. These hormonal factors interact with each other to modulate root hair development in which auxin appears to

The distribution and activity of the cell wall-loosening protein expansin is correlated with internodal growth in deepwater rice (Oryza sativa L.). Acid-induced extension of native cell walls and reconstituted extension of boiled cell walls were confined to the growing region of the internode, i.e. to the intercalary meristem (IM) and the elongation zone. Immunolocalization by tissue printing and immunoblot analysis, using antibody against cucumber expansin 29 as a probe, confirmed that rice exp

Expansins are a family of proteins capable of inducing stress relaxation of isolated cell walls. In earlier studies, we showed that the expression of expansin genes in deepwater rice (Oryza sativa L.) is regulated by developmental, hormonal and environmental stimuli. Here, we describe the spatial distribution pattern of expansin transcripts and proteins in tissues and organs of deepwater rice using in situ mRNA hybridization and immunohistochemical analysis. Expansin transcripts and proteins are

Directional cell-to-cell movement of auxin is mediated by asymmetrically localized PIN-FORMED (PIN) auxin efflux transporters. The polar localization of PINs has been reported to be modulated by phosphorylation. In this study, the function of the phosphorylation sites of the PIN3 central hydrophilic loop (HL) was characterized. The phosphorylation sites were located in two conserved neighboring motifs, RKSNASRRSF(/L) and TPRPSNL, where the former played a more decisive role than the latter. Muta

Auxin signaling is finalized by activator auxin response factors (aARFs) that are released from Auxin/Indole-3-Acetic Acid (Aux/IAA) repressors and directly activate auxin-responsive genes. However, it remains to be answered how repressor ARFs (rARFs) exert their repression function. In this study, we assessed the molecular and biological functions of two putative co-repressor-binding motifs (EAR and RLFGI) of ARF2 (a rARF) in <i>Arabidopsis thaliana</i>. In the yeast two-hybrid assay, the EAR m

PIN-FORMED (PIN)-mediated polar auxin transport (PAT) is involved in key developmental processes in plants. Various internal and external cues influence plant development via the modulation of intracellular PIN polarity and, thus, the direction of PAT, but the mechanisms underlying these processes remain largely unknown. PIN proteins harbor a hydrophilic loop (HL) that has important regulatory functions; here, we used the HL as bait in protein pulldown screening for modulators of intracellular P

Plant cell growth is restricted by the cell wall, and cell wall dynamics act as signals for the cytoplasmic and nuclear events of cell growth. Among various receptor kinases, ROOT HAIR SPECIFIC 10 (RHS10) belongs to a poorly known receptor kinase subfamily with a proline-rich extracellular domain. Here, we report that RHS10 defines the root hair length of Arabidopsis thaliana by negatively regulating hair growth. RHS10 modulates the duration of root hair growth rather than the growth rate. As po

PIN-FORMED (PIN) auxin efflux carriers with a long central hydrophilic loop (long PINs) have been implicated in organogenesis. However, the role of short hydrophilic loop PINs (short PINs) in organogenesis is largely unknown. In this study, we investigated the role of a short PIN, PIN8, in lateral root (LR) development in <i>Arabidopsis thaliana</i>. The loss-of-function mutation in <i>PIN8</i> significantly decreased LR density, mostly by affecting the emergence stage. <i>PIN8</i> showed a spor