Huo Huan Howard, Luo Ming, Lee Yuh-Ru Julie, Liu Bo
Department of Plant Biology, University of California, 1 Shields Avenue, Davis, CA 95616, USA.
Biotechnology Research Center, Southwest University, 2 Tiansheng Road, Beibei, Chongqing, China.
Plant Cell Physiol. 2025 Jul 24;66(6):890-899. doi: 10.1093/pcp/pcaf033.
The evolutionarily conserved microspherule protein 1 (MCRS1) has diverse functions, ranging from transcriptional regulation to stabilization of microtubule minus ends in acentrosomal spindles in mammals. A previous study suggested that in the model plant Arabidopsis thaliana, inactivation of an MCRS1 homolog gene led to aborted embryogenesis. To test whether this lethality was caused solely by sporophytic defects, we used the heterozygous emb1967-1/mcrs1-1 mutant for reciprocal crosses with the wild-type plant and found that the MCRS1 gene was dispensable for the development of both male and female gametophytes. An MCRS1-GFP fusion protein was expressed in the mcrs1 mutant and suppressed the mutation as evidenced by restored growth. This functional fusion protein exclusively localized to interphase nuclei and became unnoticeable during mitosis before reappearing in the reforming daughter nuclei. Affinity purification of the MCRS1-GFP protein specifically recovered the Myb-like transcription factor DRMY1 (Development Regulated Myb-like 1) but not microtubule-associated factors. Direct MCRS1-DRMY1 interaction was also demonstrated by a localization-based assay in living cells. Thus, we hypothesized that MCRS1's function was perhaps linked to transcription factors like DRMY1 and its paralog DP1 for regulation of gene expression during sporophyte development.
进化上保守的微球蛋白1（MCRS1）具有多种功能，从转录调控到哺乳动物无中心体纺锤体中微管负端的稳定。先前的一项研究表明，在模式植物拟南芥中，MCRS1同源基因的失活导致胚胎发育终止。为了测试这种致死性是否仅由孢子体缺陷引起，我们使用杂合的emb1967-1/mcrs1-1突变体与野生型植物进行正反交，发现MCRS1基因对于雄配子体和雌配子体的发育都是可有可无的。在mcrs1突变体中表达了MCRS1-GFP融合蛋白，并抑制了突变，恢复生长证明了这一点。这种功能性融合蛋白仅定位于间期细胞核，在有丝分裂期间变得不明显，然后在重新形成的子细胞核中再次出现。对MCRS1-GFP蛋白进行亲和纯化，特异性地回收了Myb样转录因子DRMY1（发育调控Myb样1），但没有回收微管相关因子。在活细胞中基于定位的分析也证明了MCRS1与DRMY1之间的直接相互作用。因此，我们推测MCRS1的功能可能与DRMY1及其旁系同源物DP1等转录因子有关，以在孢子体发育过程中调节基因表达。
