Lesion mimic mutants commonly display spontaneous cell death in pre-senescent green leaves under normal conditions, without pathogen attack. Despite molecular and phenotypic characterization of several lesion mimic mutants, the mechanisms of the spontaneous formation of cell death lesions remain largely unknown. Here, we examined the rice lesion mimic mutant spotted leaf3 (spl3). In mutants grown under a light/dark cycle, spl3 mutants appeared similar to wild type at early developmental stages, but lesions gradually appeared in the mature leaves close to heading stage. By contrast, in mutants grown under continuous light, severe cell death lesions formed in developing leaves, even at the seedling stage. Histochemical analysis showed that hydrogen peroxide accumulated in the mutants, likely causing the cell death phenotype. By map-based cloning and complementation, we showed that a 1-bp deletion in the first exon of Oryza sativa Mitogen-Activated Protein Kinase Kinase Kinase1 (OsMAPKKK1)/OsEDR1/ OsACDR1 causes the spl3 mutant phenotype. We found that the spl3 mutants were insensitive to abscisic acid (ABA), showing normal root growth in ABA-containing media and delayed leaf yellowing during dark-induced and natural senescence. Expression of ABA signaling-associated genes was also less responsive to ABA treatment in the mutants. Furthermore, the spl3 mutants had lower transcript levels and activities of catalases, which scavenge hydrogen peroxide, probably due to impairment of ABA-responsive signaling. Finally we discuss a possible molecular mechanism of lesion formation in the mature leaves of spl3 mutants.

High yield is the most important trait in various agricultural characteristics. Many approaches to improve yield have been tried in conventional agricultural practice and recently biotechnological tools employed for same goal. Genetic transformation of key genes to increase yield is one way to overcome current limitation in the field. We are producing transgenic soybean plants through high efficient transformation method by introducing all gene member with AT-hook binding domain, hoping to obtain manageable delay of senescence. Many transgenic soybean plants are growing in greenhouse and GMO field, and will be evaluated their senescence and any association with yield increase.

세포 노쇠화(cell senescence)는 나이 듦에 따른 내인성 노화 및 질병들에서 나타날 수 있는 세포의 노화인자 발현, 세포분열 정지 등의 현상으로 일컬어진다. 피부세포의 경우, 노화 및 외부요인으로 인한 세포 노쇠화가 일어나 세포분열의 정지 및 기능 이상이 관찰되며 이는 피부노화를 가속화시키는 요인이 된다. 본 연구에서는, cordycepin을 이용하여 노화된 피부세포의 세포 노쇠화 억제 및 기능 향상을 유도하여 피부노화 개선의 가능성을 제시하였다. 사람에서 유래한 섬유아세포를 이용하여 세포의 β-galactosidase 활성 세포염색 결과, 많은 계대의 세포에서 발현이 높게 나타남을 알 수 있었다. 항산화 및 항염 효과가 알려진 cordycepin을 많은 계대의 세포에 처리하였을 때 β-galactosidase 활성이 확연히 떨어짐을 확인하였고 무혈청 배지 조건에서 많은 계대 세포의 증식 및 생존율을 높이는 결과를 보였으며 세포 노쇠화와 많은 연관성이 대두되고 있는 미토콘드리아의 기능관련 실험을 진행한 결과, 높은 ROS억제능이 나타났다. 본 연구를 통하여 노화된 사람 피부 섬유아세포에서의 cordycepin의 세포 노화 개선능을 알 수 있었으며, 피부 항노화소재로서의 가능성을 확인하였다.

Plant senescence is a final process of growth and a survival strategy to use limited nutrients efficiently during development and adaptation. Tree, however, runs senescence annually for winter dormancy. Therefore understanding senescence procedure and mechanism is striking issue for tree breeding and wood productivity. In this study, we isolated a SENESCENCE 1 (PagSEN1) gene from Populus alba ⨯ P. glandulosa and determined its expressional characteristics under various conditions. The PagSEN1 encodes a putative 243 amino acid protein containing a rhodanese domain. Southern blot analysis suggested that two copies of the PagSEN1 gene are present in the poplar genome. The PagSEN1 is expressed most strongly in mature leaves but most weakly in roots. The gene is significantly up-regulated by treatment with mannitol, NaCl, ABA and JA, but not by cold, SA and GA3. These results indicate that the PagSEN1 is involved in senescence response induced by natural aging and environmental stresses. This research will provide valuable information for senescence study. To clarify SEN1 gene in poplar, we will make PagSEN1 over-expressed poplar to understand senescence procedure in detail.

The early senescence mutant was isolated from the japonica rice Koshihikari through Ethyl-methane-sulfonate (EMS) mutagenesis. The early senescence phenotype was controlled by a single recessive gene, tentatively symbolized as es-k. Using an F2 population derived from a cross between the mutant and Milyang23 and molecular markers, we mapped the es-k locus to the long arm of chromosome 7 between STS markers 147-1 and 147-2 with a physical distance of 66-kb. The symptom of early senescence appeared even before heading, while appeared during ripening in wild-type. Physiological characteristics of the es-k mutant before initiation of senescence was similar to the wild-type. However, after heading, es-k mutants started to exhibit a significant decrease in chlorophyll and soluble protein content compared to the wild-type. The wild-type leaf color appeared normal irrespective of temperature treatment, while the leaf of es-k mutant appeared pale-green at the low temperature and dark-green at the high temperature. During dark-induced senescence, mutant did not show significant differences compared to normal type. The results show that es-k is sensitive to temperature but not to light.

본 연구는 스탠다드 국화 ‘백선’의 절화를 1단계부터 6단계까지 개화단계별로 수확하여 5℃, 20℃, 35℃의 온도조건에서 48시간 수송한 후 절화의 품질과 노화정도를 비교하였다. 35℃에서 수송할 경우 5℃의 저온 수송에 비해 개화단계별로 화폭이 작았고, 1~2단계에서 수확한 절화들은 5~6단계의 것보다 크게 작았다. 또한 2~6 단계에서 수확한 절화는 수송온도가 높아질수록 최대 화폭에 도달하는데 소요되는 기간이 2~8일 늦었다. 20℃와 35℃에서 수송한 처리에 비해 5℃에서 수송한 처리가 전체 개화단계별로 생체중이 높게 유지되었다. 개화단계에 따른 용액 흡수량은 4~5단계의 절화가 가장 많은 것으로 나타났으며, 35℃의 수송온도 처리보다 5℃ 수송온도 조건에서 흡수량이 더 많았다. 20℃와 35℃에서 수송한 처리보다 5℃에서 수송한 처리가 노화가 늦게 진행되었다. 노화율이 50%되는데 소요되는 일수는 절화가 35℃에 비해 5℃에서 수송했을 때, 1단계의 절화는 4.4일, 2단계의 절화는 3일, 3~6단계의 절화는 2.7일~3.7일 연장되었다. 따라서 국내 출하용은 6단계의 절화를, 일본 수출용은 3단계의 절화를 5℃ 조건에서 수송하는 것이 절화의 품질을 유지하면서 노화를 지연시킬 수 있을 것으로 판단되었다. 는 오므려들었다. 꽃의 직경은 개화 1일째는 10시 정각에 7.6cm, 2일째는 7시 정각에 25.2cm, 3일째는 8시 정각에 23.7cm, 4일째는 10시 정각에 22.2cm로 최대치를 나타냈다. 꽃잎 수는 14개였으며, 3일째에 2개가 탈락되었으며, 4일째 12시 이전에 모두 탈락되었다. 꽃잎의 각도는 개화 1일째는 모두 직립하였으며, 1일째와 4일째는 하향된 꽃잎이 없었고, 2일째는 수평, 3일째는 직립형과 사립형이 많았다. 이와 같이 백련 꽃의 화형은 개화 후 경과 일수에 따른 각각의 특성이 뚜렷하였다. 따라서 개화 상태별로 시청각 자료나 모형을 만든 후 시청각 자료 및 모형을 보면서 개화 이력을 추적할 수 있게 하면 무안 회산지 백련은 생태체험 관광 자원으로서 활용가치가 더욱 높아질 것으로 생각된다.

본 연구는 스프레이 국화 ‘Leopard’의 절화를 1단계부터 5단계까지 개화단계별로 수확하여 5℃, 20℃, 35℃의 온도조건에서 48시간 수송한 후 절화의 품질과 노화정도를 비교하였다. 전반적으로 1, 2단계에서 수확한 절화는 5단계에서 수확한 절화에 비해 최대 화폭이 2~4mm 작은 것으로 나타나 꽃이 작음을 알 수 있었다. 수송 온도가 35℃로 높았을 때 개화가 지연되었고, 또한 처리 26일째 이후로 화폭이 급격히 작아졌다. 개화단계가 낮을수록 생체중은 가벼웠으며, 2~4단계에서 수확한 절화는 처리 후 30일까지 전반적으로 5단계의 절화에 비해 10~15g 정도 낮게 유지되었다. 또한 5℃와 20℃에서 수송한 것에 비해 35℃에서 수송한 처리에서 생체중이 크게 낮은 것으로 나타났다. 전반적으로 수송온도에 관계없이 개화가 많이 진행된 절화일수록 총 흡수량이 많았고, 수송온도가 낮을수록 절화의 총 흡수량은 증가하는 것으로 나타났다. 개화단계에 관계없이 5℃ 수송온도 조건에서 노화가 가장 늦게 진행되었으며, 35℃ 수송온도 처리에서 노화가 가장 빨리 진행되었다. 5℃와 20℃의 수송온도 처리에서는 1단계에서 수확한 절화가 5단계에 비해 노화율이 50%되는데 소요되는 일수가 각각 5.4일과 5.2일 길어졌다. 따라서 일본 수출용은 3단계의 절화를 5℃에서 수송하는 것의 절화의 품질을 유지하면서 노화를 지연시킬 수 있을 것으로 판단되었다.

Loss of leaf green color results from chlorophyll (Chl) degradation in the chloroplasts, but little is known about how Chl catabolism is tightly regulated throughout development. Using the stay-green (sgr) mutant in rice which maintains leaf greenness during senescence, we identified SGR by map-based cloning. SGR is a function-unknown gene encoding senescence-induced chloroplast protein. Transgenic rice overexpressing SGR produced yellow leaves, indicating that SGR regulates Chl degradation at the transcriptional level. Leaf stay-greenness of the sgr mutant is mainly associated with a failure in the destabilization of light-harvesting complexes (LHCs) of thylakoid membranes, which is a prerequisite event for the degradation of Chl and LHCs during leaf senescence. SGR binds to light harvesting complex of photosystem II (LHCII), but its biochemical role is so far unknown. During senescence, Chl should be degraded rapidly and safely because Chl catabolic intermediates producing ROS under light are extremely toxic to the plant cells. For safe and rapid degradation of Chl and its catabolic intermediates, Chl catabolic enzymes (CCEs) must catch the Chl intermediates effectively. In recent years, although molecular functions of SGR and CCEs have been characterized in detail, their biochemical mechanism for Chl detoxification remain elusive. Here we show that all five CCEs also specifically interact with LHCII. In addition, SGR and CCEs interact directly or indirectly with each other at LHCII, and SGR is essential for recruiting CCEs in senescing chloroplasts. These data indicate a predominant role for the SGR-CCE-LHCII protein interaction in the breakdown of LHCII-located Chl, likely to allow metabolic channeling of phototoxic Chl breakdown intermediates upstream of nontoxic pFCC.

In plant, senescence is associated with various aspects of the final stage of leaf development, nutrient relocation from leaves to reproducing seeds and stress resistance, and yield which is the most important trait in crops. Thus, the increase of knowledge on the regulatory processes of plant senescence will allow us to manipulate senescence for agronomic benefit in the future. of genetic studies have been conducted with mutants, where most of studies were focused on the delayed senescence mutants which are associated with positive factors on senescence by treating EMS to Koshikari, we induced a mutant showing early senescence phenotype, which possibly enable us to identify a negative factor of senescence. The appearance of the mutant is identical before booting stage and then the mutant showed senescence phenotype rignt before booting stage whereas Koshikari have health green leaves. The clumn length of the mutant is 98cm and the panicle length is 23cm as same as those of Koshikari. The chlorophyl contents of the mutant leaves, measured by SPAD, decreased during senescence. The soluble protein contents in the mutant leaves also decreased but no differences in the constitution reolved 1D-SDS-PAGE was detected. However, an additional shotgun proteomic approach to detect the differences of the protein constitutions during the senescence in the mutant leaves will be conducted.

The early senescence mutant was isolated from the japonica rice Koshihikari through Ethyl-methane-sulfonate(EMS) mutagenesis. The early senescence phenotype was controlled by a single recessive nuclear gene, tentatively symbolized as es-k. Using phenotypic and molecular markers, we mapped the es-k locus to the long arm of chromosome 7 between STS markers 147-1 and 150-1, a physical region of 370-kb. The symptom of early senescence appeared even before heading, while appeared after heading in those of the wild-type rice during senescence. Early stage physiological characteristics of the es-k mutant was similar to that of the wild-type. However, after heading, es-k mutants started to exhibit a significant decrease in chlorophyll content, soluble protein content 10 days earlier compared to normal type. To characterize the interaction with the environment factors, experiments were carried out under controlled temperature and light conditions, respectively. The wild-type leaf color appeared normal irrespective of temperature treatment, while the leaf of es-k mutant appeared pale-green at the low temperature and dark-green at the high temperature. During dark-induced senescence, mutant did not show significant differences compared to normal type. The results show that es-k is sensitive to temperature but not to light.

Activity of senescence-induced antioxidant enzymes in the detached rice seedlings (Oryza sativa L. cv. Dongjin) was examined. The levels of ~textrmH2~textrmO2 content and peroxidase (POD) activity were gradually increased during leaf senescence, whereas catalase activity was decreased. The activity of superoxide dismutase (SOD) was increased, and ascorbate peroxidase (APX) and glutathione reductase (GR) were slightly increased until 3d and 4d of dark induced-senescence, and thereafter were decreased. The activation of all SOD isoforms showed a significant decrease after 6d and 7d. After 4d to 7d of dark senescence, there was a significant effect in enhancing the activity of APX-12 and -13 isoforms as compared with light, despite similar levels in total APX activity. GR-8 and -10 isoforms were more effective in leaf senescence at 4d to 7d, particularly with respect to dark-induced senescence. These results suggest that the metabolism of active oxygen species such as ~textrmH2~textrmO2 is dependent on various functionally interrelated antioxidant enzymes such as catalase, peroxidase, SOD, APX and GR.

This study was conducted to investigate the varietal differences in leaf senescence during ripening stage and its relation to grain yield of rice. During grain filling period leaf senescence was evaluated by SPAD readings (an indirect indicator of chlorophyll content) for 74 varieties including local, improved domestic, and introduced varieties in the field condition. Leaf senescence was varied greatly among 74 varieties. Jodongji and Dadajo known as local rice varieties had significantly lower SPAD value than the other varieties and became senescent rapidly. However, SPAD value of the flag leaf and 2nd leaf of SNU-SG1 were much higher than the other varieties and leaves of SNU-SG1 also showed a tendency of delayed senescence compared to the other varieties. There were significantly positive correlation between cumulated SPAD value of upper leaf(flag leaf and 2nd leaf) during 35 days after heading and grain yield divided by sunshine hour during 40 days of grain filling and compensated for temperature effect, and cumulated SPAD value of the 4th leaf showed negative correlation with the yield. That is, the delayed senescence of the upper leaves and the rapid senescence of lower leaves were positively associated with grain yield increase.

This study was conducted to investigate the varietal differences in leaf senescence and the relationship between leaf senescence and photosynthesis during ripening stage of rice. During grain filling period, leaf senescence was evaluated by SPAD readings (an indirect indicator of chlorophyll content) for 3 rice varieties (SNU-SG1, Hwaseongbyeo, Nampungbyeo). SPAD value of flag leaf and 2nd leaf of SNU-SG1 were much higher than the other varieties and the leaves of SNU-SG1 also showed a tendency of delayed senescence as compared to the other varieties. Photosynthesis at light saturation (Pmax) of flag, 2nd and 3rd leaf in SNU-SG1 during grain filling period were much higher than Hwaseongbyeo and Nampungbyeo. The Pmax of the flag leaf in SNU-SG1 was especially higher over 20% than the other varieties. It was due to its higher mesophyll conductance and stomatal conductance as compared to the other varieties. Pmax, stomatal conductance and mesophyll conductance had positive correlation with SPAD value and nitrogen concentration of leaves. In conclusion, the stay green characteristics of SNU-SG1 would contribute to increasing the grain yield through the improved photosynthesis during grain filling.