Plant Research International, Bioscience, 6700 AP Wageningen, The Netherlands.
Plant Cell. 2014 Jan;26(1):195-209. doi: 10.1105/tpc.113.116491. Epub 2014 Jan 24.
The haploid male gametophyte, the pollen grain, is a terminally differentiated structure whose function ends at fertilization. Plant breeding and propagation widely use haploid embryo production from in vitro-cultured male gametophytes, but this technique remains poorly understood at the mechanistic level. Here, we show that histone deacetylases (HDACs) regulate the switch to haploid embryogenesis. Blocking HDAC activity with trichostatin A (TSA) in cultured male gametophytes of Brassica napus leads to a large increase in the proportion of cells that switch from pollen to embryogenic growth. Embryogenic growth is enhanced by, but not dependent on, the high-temperature stress that is normally used to induce haploid embryogenesis in B. napus. The male gametophyte of Arabidopsis thaliana, which is recalcitrant to haploid embryo development in culture, also forms embryogenic cell clusters after TSA treatment. Genetic analysis suggests that the HDAC protein HDA17 plays a role in this process. TSA treatment of male gametophytes is associated with the hyperacetylation of histones H3 and H4. We propose that the totipotency of the male gametophyte is kept in check by an HDAC-dependent mechanism and that the stress treatments used to induce haploid embryo development in culture impinge on this HDAC-dependent pathway.
单倍体雄性配子体，花粉粒，是一个终末分化的结构，其功能在受精时结束。植物的繁殖和繁殖广泛利用体外培养的雄性配子体产生的单倍体胚胎，但这种技术在机制水平上仍然知之甚少。在这里，我们表明组蛋白去乙酰化酶（HDACs）调节向单倍体胚胎发生的转变。用曲古抑菌素 A（TSA）阻断 Brassica napus 培养的雄性配子体中的 HDAC 活性会导致大量细胞从花粉转变为胚胎发生生长。胚胎发生生长通过但不依赖于通常用于诱导 B. napus 单倍体胚胎发生的高温胁迫得到增强。拟南芥雄性配子体在培养中对单倍体胚胎发育具有抗性，但在 TSA 处理后也会形成胚胎发生细胞簇。遗传分析表明，HDAC 蛋白 HDA17 在这个过程中起作用。雄性配子体的 TSA 处理与组蛋白 H3 和 H4 的乙酰化过度有关。我们提出，雄性配子体的全能性受到 HDAC 依赖性机制的控制，而用于诱导培养中单倍体胚胎发育的应激处理会影响这种 HDAC 依赖性途径。
