Twilight-zone and canopy shade induction of the Athb-2 homeobox gene in green plants
Twilight-zone and canopy shade induction of the Athb-2 homeobox gene in green plants
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DOI：
10.1073/pnas.93.8.3530
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发表时间：
1996-04-16
影响因子：
11.1
通讯作者：
Ruberti, I
中科院分区：
文献类型：
--
作者：
Carabelli, M;Morelli, G;Ruberti, I
我们提供的证据表明，一种在绿色植物中起作用的新型光敏色素（除光敏色素 A 和 B、PHYA 和 PHYB 之外）可调节植物同源盒基因 (Athb-2) 的“暮光诱导”表达。 Athb-2 基因的光调节是独特的，因为它不是由富含红色 (R) 的日光或明暗转变诱导的，而是由 R 与远红 (FR) 光的比例变化诱导的。这些变化通常发生在黎明和黄昏（日终 FR），也发生在白天的树冠下（避荫）。通过使用纯光源和phyA/phyB无效突变体，我们证明了通过R/FR比的变化诱导Athb-2在很大程度上是由在绿色植物中起作用的新型光敏色素介导的。此外，PHYB 在抑制黑暗中 Athb-2 mRNA 积累方面发挥负面作用，在 FR 反应中发挥次要作用。 Athb-2 表达与 FR 诱导的生长现象的严格相关性表明 Athb-2 基因在介导细胞伸长中的作用。Athb-2 基因在快速伸长的黄化幼苗中高水平表达的发现支持了这种解释。此外，由于 R 光或 FR 光抑制黄化组织中的细胞伸长，它们也会下调 Athb-2 mRNA 的表达。因此，这些数据支持这样的观点，即新型光敏色素感知的光质量变化通过 Athb-2 同源盒基因的作用调节植物发育。
We present evidence that a novel phytochrome (other than phytochromes A and B, PHYA and PHYB) operative in green plants regulates the ''twilight-inducible'' expression of a plant homeobox gene (Athb-2). Light regulation of the Athb-2 gene is unique in that it is not induced by red (R)-rich daylight or by the light-dark transition but is instead induced by changes in the ratio of R to far-red (FR) light. These changes, which normally occur at dawn and dusk (end-of-day FR), also occur during the daytime under the canopy (shade avoidance). By using pure light sources and phyA/phyB null mutants, we demonstrated that the induction of Athb-2 by changes in the R/FR ratio is mediated for the most part by a novel phytochrome operative in green plants. Furthermore, PHYB plays a negative role in repressing the accumulation of Athb-2 mRNA in the dark and a minor role in the FR response. The strict correlation of Athb-2 expression with FR-induced growth phenomena suggests a role for the Athb-2 gene in mediating cell elongation, This interpretation is supported by the finding that the Athb-2 gene is expressed at high levels in rapidly elongating etiolated seedlings. Furthermore, as either R or FR light inhibits cell elongation in etiolated tissues, they also down-regulate the expression of Athb-2 mRNA. Thus, these data support the notion that changes in light quality perceived by a novel phytochrome regulate plant development through the action of the Athb-2 homeobox gene.