Gagliardi D, Breton C, Chaboud A, Vergne P, Dumas C
Ecole Normale Supérieure de Lyon, Reconnaissance Cellulaire et Amélioration des Plantes, UMR CNRS-INRA 9938, Lyon, France.
Plant Mol Biol. 1995 Nov;29(4):841-56. doi: 10.1007/BF00041173.
We have analysed the expression of heat shock protein 70 (HSP70) and heat shock factor (HSF) gene during maize pollen development, HSFs being the transcriptional activators of hsp genes. In order to eliminate the sporophytic tissues of anthers, we have isolated homogeneous cell populations corresponding to five stages of maize pollen development from microspores to mature pollen. We show that in the absence of heat stress, hsp70 genes are highly expressed late-bicellular pollen as compared to other stages. HSP70 transcripts are significantly accumulated in response to a heat shock at the late microspore stage but to a much lower extent than in vegetative tissues. The latest stages of pollen development, i.e. mid-tricellular and mature pollen, do not exhibit heat-induced accumulation of HSP70 transcripts. Therefore, we analysed the expression of hsf genes throughout pollen development. We demonstrate that at least three hsf genes are expressed in maize and that transcripts corresponding to one hsf gene, whose expression is independent of temperature in somatic as well as in microgametophytic tissues, are present at similar levels throughout pollen development. In addition, we show that the expression of the two other hsf genes is heat-inducible in maize vegetative tissues and is not significantly increased after heat shock at any stage of pollen development. These results indicate that the loss of hsp gene expression at late stages of pollen development is not due to a modification of hsf gene expression at the mRNA level and that hsf gene expression is differentially regulated in vegetative and microgametophytic tissues.
我们分析了热休克蛋白70（HSP70）和热休克因子（HSF）基因在玉米花粉发育过程中的表达情况，其中热休克因子是热休克蛋白基因的转录激活因子。为了去除花药的孢子体组织，我们从微孢子到成熟花粉分离出了与玉米花粉发育五个阶段相对应的同质细胞群体。我们发现，在没有热胁迫的情况下，与其他阶段相比，hsp70基因在晚期二细胞花粉中高度表达。HSP70转录本在小孢子晚期热休克处理后显著积累，但积累程度远低于营养组织。花粉发育的最后阶段，即中期三细胞花粉和成熟花粉，未表现出热诱导的HSP70转录本积累。因此，我们分析了热休克因子基因在整个花粉发育过程中的表达。我们证明，玉米中至少有三个热休克因子基因表达，并且与一个热休克因子基因相对应的转录本在整个花粉发育过程中以相似水平存在，其在体细胞和小配子体组织中的表达均与温度无关。此外，我们发现另外两个热休克因子基因的表达在玉米营养组织中是热诱导的，并且在花粉发育的任何阶段热休克处理后均未显著增加。这些结果表明，花粉发育后期热休克蛋白基因表达的丧失并非由于热休克因子基因在mRNA水平上的表达改变，并且热休克因子基因在营养组织和小配子体组织中的表达受到不同的调控。
