高温影响番茄小孢子发育的细胞学研究

Cytological study on microsporogenesis of Solanum lycopersicum var. Micro-Tom under high temperature stress

以番茄‘Micro-Tom’为材料,利用形态观察、DAPI染色、石蜡切片等方法对正常情况下番茄小孢子发生过程进行时期划分。通过连续7 d的高温胁迫((35±1)℃/(30±1)℃)处理试验,结合细胞学观察,研究高温对番茄花粉小孢子发育的影响。研究表明,高温胁迫不仅导致花粉畸形或败育、花粉数量减少、活力低萌发力差,而且还导致花药绒毡层、药隔组织、药室内壁、花药表皮、环状细胞簇等花药细胞结构的发育异常。结果有助于阐明热胁迫对番茄小孢子发育的影响,并为培育耐高温农作物新品种提供思路。

Tomato （Solanum lycopersicum）, one of the most important vegetables, is susceptible to high-temperature injury High temperature adversely affects its anther development and fertilization, resuting in poor fertilization and fruit set. Therefore, the present study aimed to examine the cellular morphology of anther development and microsporogenesis under optimal and high temperature conditions in a miniature dwarf tomato cultivar, Micro-Tom, a preferred variety for genetic and genomic studies. Based on morphological observation, DAPI staining and anatomical study, the microsporogenesis process of tomato anther could be divided into six stages including premeiotic, tetrad, early uninucleate microspore, vacuolated microspore, binucleate pollen, and mature pollen grain stage. Meanwhile, a defined correlation was found between the flower bud size and the stage of pollen development under optimal conditions, which makes possible the accurate prediction of anther and pollen development stages for the reproductive study. Subsequently, the effect of high temperature stress on the microsporogenesis was checked by the paraffin section assay and pollen viability test, using the flowering plants successively exposed to high temperature （ （35 ＋ 1 ） °C / （ 30 ＋ 1 ） °C, day/night） for 7 days. The results showed that high temperature exposure induced the abnormity of early pollen or the abortion of pollen maturation, leading to the reduction of pollen number and decrease of pollen viability. So the anthers failed to develop maturity pollen under high temperature stress, thereby causing reduced tomato yields. Furthermore, cytological analysis of anther development in tomato plants under different temperature during 6 different periods showed that there was no significant difference in anthers structure between high temperature-treated and control plants at early microspore developmental stages. Their difference was firstly observed at the tetrad stage. The tapetal cells, the innermost cell layer of the anther wall, began to swell under hightemperature stress. In the later stage, this abnormal swelling further dilated into led to delay degrading of tapetum as well. Since tapetum supplied nutrients the locular space. On the other hand, it and several enzymes required for pollen development, pollen mother cells stopped to develop into pollen. At the later development stage, the abnormality of connective tissue, endothecium, epidermis, stomium and circular cell cluster was also observed during pollen development. Our data indicated that male sterility under high temperature might be mainly due to malfunctioning of the tapetum resulting in defects in pollen development. The present results will help to understand the basic mechanisms of anther development and microsporogenesis under high temperature condition in tomato.