OsNAP

| Categories genes  | Tags grain  ABA  senescence  ja  yield  flower  abiotic stress  transcription factor  leaf  salinity  drought  seedling  jasmonic  temperature  growth  jasmonic acid  vegetative  abscisic acid  leaf senescence  abscisic acid biosynthesis  grain-filling 
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    • OsNAP-overexpressing transgenic plants displayed an accelerated leaf senescence phenotype at the grain-filling stage, which might be caused by the elevated JA levels and the increased expression of the JA biosynthesis-related genes LOX2 and AOC1, and showed enhanced tolerance ability to MeJA treatment at the seedling stage
    • Analysis of the OsNAP transcript levels in rice showed that this gene was significantly induced by ABA and abiotic stresses, including high salinity, drought and low temperature
    • The NAC family transcription factor OsNAP confers abiotic stress response through the ABA pathway
    • RESULTS: In this study, we reported a member of the NAC transcription factor family named OsNAP whose expression is associated with leaf senescence, and investigated its preliminary function during the process of leaf senescence
    • The results of qRT-PCR showed that the OsNAP transcripts were accumulated gradually in response to leaf senescence and treatment with methyl jasmonic acid (MeJA)
    • Nevertheless, the leaf senescence process was delayed in OsNAP RNAi transgenic plants with a dramatic drop in JA levels and with decreased expression levels of the JA biosynthesis-related genes AOS2, AOC1 and OPR7
    • CONCLUSIONS: These results suggest that OsNAP acts as a positive regulator of leaf senescence and this regulation may occur via the JA pathway
    • Rice plants overexpressing OsNAP did not show growth retardation, but showed a significantly reduced rate of water loss, enhanced tolerance to high salinity, drought and low temperature at the vegetative stage, and improved yield under drought stress at the flowering stage
    • Our data suggest that OsNAP functions as a transcriptional activator that plays a role in mediating abiotic stress responses in rice
    • OsNAP is a member of the NAC transcription factor family; it is localized in the nucleus, and shows transcriptional activator activity in yeast
    • Microarray analysis of transgenic plants overexpressing OsNAP revealed that many stress-related genes were up-regulated, including OsPP2C06/OsABI2, OsPP2C09, OsPP2C68 and OsSalT, and some genes coding for stress-related transcription factors (OsDREB1A, OsMYB2, OsAP37 and OsAP59)
    • OsNAP connects abscisic acid and leaf senescence by fine-tuning abscisic acid biosynthesis and directly targeting senescence-associated genes in rice
    • Additionally, reduced OsNAP expression leads to delayed leaf senescence and an extended grain-filling period, resulting in a 6.3% and 10.3% increase in the grain yield of two independent representative RNAi lines, respectively.
    • Thus, fine-tuning OsNAP expression should be a useful strategy for improving rice yield in the future
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