http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
전상은,김경태,Yoko Okushima,남재성,Masaaki Umeda 한국분자세포생물학회 2013 Molecules and cells Vol.35 No.1
The cell cycle plays an important role in the development and adaptation of multicellular organisms; specifically, it allows them to optimally adjust their architecture in re-sponse to environmental changes. Kip-related proteins (KRPs) are important negative regulators of cyclin-depen-dent kinases (CDKs), which positively control the cell cycle during plant development. The Arabidopsis genome possesses seven KRP genes with low sequence similarity and distinct expression patterns; however, why Arabidopsis needs seven KRP genes and how these genes function in cell cycle regulation are unknown. Here, we focused on the characterization of KRP3, which was found to have unique functions in the shoot apical meristem (SAM) and leaves. KRP3 protein was localized to the SAM, including the ground meristem and vascular tissues in the ground part of the SAM and cotyledons. In addition, KRP3 protein was stabilized when treated with MG132, an inhibitor of the 26S proteasome, indicating that the protein may be regulated by 26S proteasome-mediated protein degradation. KRP3-overexpressing (KRP3 OE) transgenic plants showed reduced organ size, serrated leaves, and reduced fertility. Interestingly, the KRP3 OE transgenic plants showed a significant reduction in the size of the SAM with alterations in cell arrangement. In addition, compared to the wild type, the KRP3 OE transgenic plants had a higher DNA ploidy level in the SAM and leaves. Taken together, our data suggest that KRP3 plays important regulatory roles in the cell cycle and endoreduplication in the SAM and leaves.
Takahashi, N.,Kajihara, T.,Okamura, C.,Kim, Y.,Katagiri, Y.,Okushima, Y.,Matsunaga, S.,Hwang, I.,Umeda, M. Current Biology Ltd ; Elsevier Science Ltd 2013 Current biology Vol.23 No.18
Plant roots respond to various internal and external signals and adjust themselves to changes of environmental conditions. In the root meristem, stem cells produce daughter cells that continue to divide several times. When these latter cells reach the transition zone, they stop dividing and enter the endocycle, a modified cell cycle in which DNA replication is repeated without mitosis or cytokinesis. The resultant DNA polyploidization, named endoreduplication, is usually associated with an increase of nuclear and cell volume and with cell differentiation [1-4]. At the transition zone, cytokinin signaling activates two transcription factors, type-B ARABIDOPSIS RESPONSE REGULATOR 1 (ARR1) and ARR12, and induces SHY2/IAA3, a member of the Aux/IAA family of auxin signaling repressors. This inhibits auxin signaling and reduces the expression of auxin efflux carriers, resulting in cell division arrest [5]. Such counteracting actions of two hormones are assumed to determine meristem size. However, it remains unknown whether cytokinins additionally control meristem size through an auxin-independent pathway. Here we show that, in Arabidopsis, the cytokinin-activated ARR2 directly upregulates the expression of CCS52A1, which encodes an activator of an E3 ubiquitin ligase, anaphase-promoting complex/cyclosome (APC/C) [6], thereby promoting the onset of the endocycle and restricting meristem size. Our genetic data revealed that CCS52A1 function is independent of SHY2-mediated control of auxin signaling, indicating that downregulation of auxin signaling and APC/C-mediated degradation of cell-cycle regulators cooperatively promote endocycle onset, and thus fine tune root growth.