Méndez-Vigo Belén, Arteaga Noelia, Murillo-Sánchez Alba, Alba Sonia, Alonso-Blanco Carlos
Departamento de Genética Molecular de Plantas, Centro Nacional de Biotecnología (CNB), Consejo Superior de Investigaciones Científicas (CSIC), Madrid 28049, Spain.
Plant Physiol. 2024 Dec 23;197(1). doi: 10.1093/plphys/kiae673.
The number and distribution of trichomes, i.e. the trichome pattern, in different plant organs show a conspicuous inter- and intraspecific diversity across Angiosperms that is presumably involved in adaptation to numerous environmental factors. The genetic and molecular mechanisms accounting for the evolution of trichome patterns have just begun to be elucidated. In this study, we aimed to identify and characterize MALAMBRUNO 1 (MAU1), a locus affecting trichome number in the fruits of Arabidopsis (Arabidopsis thaliana) natural populations. To this end, we developed introgression lines (ILs) from the hairy fruit accession Doñana (Don-0) in the genetic background of the Ler strain with glabrous fruits. Genetic analyses of ILs showed that MAU1 affects fruit trichome patterns through synergistic epistasis with the MYB genes TRICHOMELESS1 (TCL1), GLABRA1 (GL1), and TRIPTYCHON (TRY). In addition, fine mapping and characterization of transgenic lines demonstrated that MAU1 is the bHLH transcription factor gene EGL3, for which Don-0 carries a gain-of-function semidominant allele. Gene expression analyses did not detect differences between EGL3 alleles, thus supporting that a structural missense mutation is the causal nucleotide polymorphism of Don-0. Further phylogenetic analyses of EGL3 showed that most Arabidopsis populations with hairy fruits belong to 3 haplogroups, suggesting that additional EGL3 natural alleles account for fruit trichome development. Finally, the characterization of EGL3 pleiotropy indicates that Don-0 hyperfunction also increases stem trichome branching. We conclude that EGL3 interactions in the core gene regulatory network of trichome development explain the Arabidopsis natural diversity for fruit trichome pattern and morphology.
不同植物器官中毛状体的数量和分布，即毛状体模式，在被子植物中表现出明显的种间和种内多样性，这可能与适应多种环境因素有关。解释毛状体模式进化的遗传和分子机制才刚刚开始被阐明。在本研究中，我们旨在鉴定和表征MALAMBRUNO 1（MAU1），这是一个影响拟南芥（Arabidopsis thaliana）自然种群果实中毛状体数量的基因座。为此，我们以果实无毛的Ler品系为遗传背景，从多毛果实的Doñana（Don-0）材料中培育了导入系（ILs）。对导入系的遗传分析表明，MAU1通过与MYB基因TRICHOMELESS1（TCL1）、GLABRA1（GL1）和TRIPTYCHON（TRY）的协同上位性作用影响果实毛状体模式。此外，对转基因系的精细定位和表征表明，MAU1是bHLH转录因子基因EGL3，Don-0携带该基因的一个功能获得性半显性等位基因。基因表达分析未检测到EGL3等位基因之间的差异，因此支持结构错义突变是Don-0的因果核苷酸多态性。对EGL3的进一步系统发育分析表明，大多数果实有毛的拟南芥种群属于3个单倍群，这表明EGL3还有其他自然等位基因参与果实毛状体的发育。最后，对EGL3多效性的表征表明，Don-0的功能亢进还增加了茎上毛状体的分支。我们得出结论，EGL3在毛状体发育核心基因调控网络中的相互作用解释了拟南芥果实毛状体模式和形态的自然多样性。
