Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
Curr Biol. 2011 Aug 9;21(15):1277-81. doi: 10.1016/j.cub.2011.07.001. Epub 2011 Jul 28.
Morphogenesis of seed plants commences with highly stereotypical cell division sequences in early embryogenesis [1, 2]. Although a small number of transcription factors and a mitogen-activated protein (MAP) kinase cascade have been implicated in this process [3-8], pattern formation in early embryogenesis remains poorly understood. We show here that the Arabidopsis RKD4, a member of the RWP-RK motif-containing putative transcription factors [9], is required for this process. Loss-of-function rkd4 mutants were defective in zygotic cell elongation, as well as subsequent cell division patterns. As expected from this mutant phenotype, RKD4 was transcribed preferentially in early embryos. RKD4 possessed functional characteristics of transcription factors and was able to ectopically induce early embryo-specific genes when overexpressed in seedlings. Strikingly, induced overexpression of RKD4 primed somatic cells for embryogenesis independently of external growth regulators. These results reveal that RKD4 is a novel key regulator of the earliest stage of plant development.
种子植物的形态发生始于早期胚胎发生中高度定型的细胞分裂序列[1,2]。尽管已有少数转录因子和丝裂原活化蛋白（MAP）激酶级联反应被牵连到这一过程中[3-8]，但早期胚胎发生中的模式形成仍知之甚少。我们在此表明，拟南芥 RKD4 是 RWP-RK 基序包含的假定转录因子的成员[9]，对于这个过程是必需的。功能丧失的 rkd4 突变体在合子细胞伸长以及随后的细胞分裂模式方面存在缺陷。正如从该突变体表型所预期的那样，RKD4 在早期胚胎中优先转录。RKD4 具有转录因子的功能特性，并且在幼苗中过表达时能够异位诱导早期胚胎特异性基因。引人注目的是，RKD4 的过表达诱导使体细胞在独立于外部生长调节剂的情况下为胚胎发生做好准备。这些结果表明，RKD4 是植物发育最早阶段的一个新的关键调节因子。
