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Microspore embryogenesis (ME) is a process in which the gametophytic pollen programme of the microspore is reoriented towards a new embryo sporophytic programme. This process requires a stress treatment, usually performed in the anther or isolated microspores for several days. Despite the universal use of stress to induce ME, very few studies have addressed the physiological processes that occur in the anther during this step. To further understand the processes triggered by stress treatment, we followed the response of anthers by measuring the expression of stress-related genes in two barley (Hordeum vulgare L.) cultivars differing in their ME response. Genes encoding enzymes involved in oxidative stress (glutathione-S-transferase, GST; oxalate oxidase, OxO), in the synthesis of jasmonic acid (13-lipoxygenase, Lox; allene oxide cyclase, AOC; allene oxide synthase, AOS) and in the phenylpropanoid pathway (phenylalanine ammonia lyase, PAL), as well as those encoding PR proteins (Barwin, chitinase 2b, Chit 2b; glucanase, Gluc; basic pathogenesis-related protein 1, PR1; pathogenesis-related protein 10, PR10) were up-regulated in whole anthers upon stress treatment, indicating that anther perceives stress and reacts by triggering general plant defence mechanisms. In particular, both OxO and Chit 2b genes are good markers of anther reactivity owing to their high level of induction during the stress treatment. The effect of copper sulphate appeared to limit the expression of defence-related genes, which may be correlated with its positive effect on the yield of microspore embryos.

To characterize the spatial and temporal occurrence of programmed cell death (PCD) in Lilium anther tissues, we used both microscopical and molecular markers of apoptosis for developmental stages from meiosis to pollen release. The first hallmarks of PCD include cell condensation and shrinkage of the cytoplasm, separation of chromatin into delineated masses, and DNA fragmentation in the tapetum as early as the premeiosis stage. PCD then extended to other anther sporophytic tissues, leading to anther dehiscence. Although the PCD clearly affected the endothecium and the epidermis, these two cell layers remained alive until anther dehiscence. In pollen, no sign of PCD was found until pollen mitosis I, after what apoptotic features developed progressively in the vegetative cell. In addition, DNA ladders were detected in all sporophytic tissues and cell types throughout pollen development, whereas in the male gametophyte DNA ladders were only detected during pollen maturation. Our data suggest that PCD is a progressive and active process affecting all the anther tissues, first being triggered in the tapetum.

Microspore embryogenesis (ME) is a process in which the gametophytic pollen programme of the microspore is reorientated towards a new embryo sporophytic programme. This process requires a stress treatment, usually performed in the anther or isolated microspores for several days. Despite the universal use of stress to induce ME, very few studies have addressed the physiological processes that occur in the anther during this step. To further understand the processes triggered by stress treatment, we followed the response of anthers by measuring the expression of stress-related genes in two barley ( Hordeum vulgare L.) cultivars differing in their ME response. Genes encoding enzymes involved in oxidative stress ( glutathione-S-transferase, GST; oxalate oxidase, OxO), in the synthesis of jasmonic acid ( 13-lipoxygenase, Lox; allene oxide cyclase, AOC; allene oxide synthase, AOS) and in the phenylpropanoid pathway ( phenylalanine ammonia lyase, PAL), as well as those encoding PR proteins ( Barwin, chitinase 2b, Chit 2b; glucanase, Gluc; basic pathogenesis-related protein 1, PR1; pathogenesis-related protein 10, PR10) were up-regulated in whole anthers upon stress treatment, indicating that anther perceives stress and reacts by triggering general plant defence mechanisms. In particular, both OxO and Chit 2b genes are good markers of anther reactivity owing to their high level of induction during the stress treatment. The effect of copper sulphate appeared to limit the expression of defence-related genes, which may be correlated with its positive effect on the yield of microspore embryos. [ABSTRACT FROM AUTHOR]