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拟南芥种子休眠的丧失与GID1赤霉素激素受体积累的增加有关。

Loss of Arabidopsis thaliana Seed Dormancy is Associated with Increased Accumulation of the GID1 GA Hormone Receptors.

作者信息

Hauvermale Amber L, Tuttle Keiko M, Takebayashi Yumiko, Seo Mitsunori, Steber Camille M

机构信息

Department of Crop and Soil Science, Washington State University, Pullman, WA 99164-6420, USA.

Molecular Plant Sciences Program, Washington State University, Pullman, WA 99164-6420, USA.

出版信息

Plant Cell Physiol. 2015 Sep;56(9):1773-85. doi: 10.1093/pcp/pcv084. Epub 2015 Jul 1.

Abstract

Dormancy prevents seeds from germinating under favorable conditions until they have experienced dormancy-breaking conditions, such as after-ripening through a period of dry storage or cold imbibition. Abscisic acid (ABA) hormone signaling establishes and maintains seed dormancy, whereas gibberellin (GA) signaling stimulates germination. ABA levels decrease and GA levels increase with after-ripening and cold stratification. However, increasing GA sensitivity may also be critical to dormancy loss since increasing seed GA levels are detectable only with long periods of after-ripening and imbibition. After-ripening and cold stratification act additively to enhance GA hormone sensitivity in ga1-3 seeds that cannot synthesize GA. Since the overexpression of the GA receptor GID1 (GIBBERELLIN-INSENSITIVE DWARF1) enhanced this dormancy loss, and because gid1a gid1b gid1c triple mutants show decreased germination, the effects of dormancy-breaking treatments on GID1 mRNA and protein accumulation were examined. Partial after-ripening resulted in increased GID1b, but not GID1a or GID1c mRNA levels. Cold imbibition stimulated the accumulation of all three GID1 transcripts, but resulted in no increase in GA sensitivity during ga1-3 seed germination unless seeds were also partially after-ripened. This is probably because after-ripening was needed to enhance GID1 protein accumulation, independently of transcript abundance. The rise in GID1b transcript with after-ripening was not associated with decreased ABA levels, suggesting there is ABA-independent GID1b regulation by after-ripening and the 26S proteasome. GA and the DELLA RGL2 repressor of GA responses differentially regulated the three GID1 transcripts. Moreover, DELLA RGL2 appeared to switch between positive and negative regulation of GID1 expression in response to dormancy-breaking treatments.

摘要

休眠可防止种子在适宜条件下萌发,直到它们经历了打破休眠的条件,比如经过一段时间的干燥储存或冷浸吸胀后完成后熟。脱落酸(ABA)激素信号建立并维持种子休眠,而赤霉素(GA)信号则刺激种子萌发。随着后熟和低温层积,ABA水平下降,GA水平上升。然而,提高GA敏感性对于休眠丧失可能也至关重要,因为只有经过长时间的后熟和浸吸胀才能检测到种子GA水平的增加。后熟和低温层积共同作用,可增强无法合成GA的ga1-3种子对GA激素的敏感性。由于GA受体GID1(赤霉素不敏感矮化1)的过表达增强了这种休眠丧失,并且因为gid1a gid1b gid1c三突变体的萌发率降低,所以研究了打破休眠处理对GID1 mRNA和蛋白质积累的影响。部分后熟导致GID1b mRNA水平增加,但GID1a或GID1c mRNA水平未增加。冷浸吸胀刺激了所有三种GID1转录本的积累,但在ga1-3种子萌发期间,除非种子也经过部分后熟,否则GA敏感性不会增加。这可能是因为后熟需要增强GID1蛋白质积累,而与转录本丰度无关。后熟导致的GID1b转录本增加与ABA水平降低无关,这表明后熟和26S蛋白酶体对GID1b存在不依赖ABA的调控。GA和GA反应的DELLA阻遏物RGL2对三种GID1转录本有不同的调控作用。此外,DELLA RGL2似乎会根据打破休眠的处理方式,在对GID1表达的正调控和负调控之间切换。

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