Truncation of LEAFY COTYLEDON1 Protein Is Required for Asexual Reproduction in Kalanchoë daigremontiana

Abstract

Kalanchoë daigremontiana reproduces asexually by generating numerous plantlets on its leaf margins. The formation of plantlets requires the somatic initiation of organogenic and embryogenic developmental programs in the leaves. However, unlike normal embryogenesis in seeds, leaf somatic embryogenesis bypasses seed dormancy to form viable plantlets. In Arabidopsis (Arabidopsis thaliana), seed dormancy and embryogenesis are initiated by the transcription factor LEAFY COTYLEDON1 (LEC1). The K. daigremontiana ortholog of LEC1 is expressed during leaf somatic embryo development. However, KdLEC1 encodes for a LEC1-type protein that has a unique B domain, with 11 unique amino acids and a premature stop codon. Moreover, the truncated KdLEC1 protein is not functional in Arabidopsis. Here, we show that K. daigremontiana transgenic plants expressing a functional, chimeric KdLEC1 gene under the control of Arabidopsis LEC1 promoter caused several developmental defects to leaf somatic embryos, including seed dormancy characteristics. The dormant plantlets also behaved as typical dormant seeds. Transgenic plantlets accumulated oil bodies and responded to the abscisic acid biosynthesis inhibitor fluridone, which broke somatic-embryo dormancy and promoted their normal development. Our results indicate that having a mutated form of LEC1 gene in K. daigremontiana is essential to bypass dormancy in the leaf embryos and generate viable plantlets, suggesting that the loss of a functional LEC1 promotes viviparous leaf somatic embryos and thus enhances vegetative propagation in K. daigremontiana. Mutations resulting in truncated LEC1 proteins may have been of a selective advantage in creating somatic propagules, because such mutations occurred independently in several Kalanchoë species, which form plantlets constitutively.

Incomplete reprogramming of cell-specific epigenetic marks during asexual reproduction leads to heritable phenotypic variation in plants

“…Specifically, we created somatic embryos from distinct root (Root Origin, RO) and leaf (Leaf Origin, RO) tissues of Arabidopsis thaliana (Col-0 strain) by the controlled expression of a RWP-RK zygotic factor [9] ( Supplementary Fig. 1), in order to mimic naturally-occurring events associated with asexual propagation [2,10]. We collected seeds from independently regenerated G0 individuals after self-pollination and further propagated each line by selfing for over three consecutive generations (G1-G3) ( Fig.…”

Recent progress on plant regeneration

“…B3结构 域蛋白VAL1 (VP1/ABI3-LIKE1)和VAL2 [109] 能够通 过和PRC1相互作用后招募PRC1抑制胚胎特征基因 的表达 [110] . PKL也具有抑制胚胎发育特征基因的能 力 , 其 突 变 体 表 现 出 胚 后 发 育 的 根 部 出 现 胚 胎 特 [117,118] . 对大叶落地生根(Kalanchoё daigre- montiana)的研究发现, 在这一脱分化过程中, 可以 检测到两类基因的表达 [117] .…”

Efectos del ácido giberélico, bencilaminopurina y fluridona en la germinación in vitro de Ugni molinae Turcz. (Myrtaceae)

“…Los carotenoides son los principales precursores del ABA en plantas, por lo tanto, la inhibición de la carotenogénesis también implica impedir la biosíntesis de ABA. Muchos investigadores han encontrado en inhibidores de ABA, como fluridona y norfluorazon, comúnmente utilizados como herbicidas (Sun et al 2012), una herramienta útil para estudios de germinación y rompimiento de la dormancia tanto para embriones cigóticos (Popova 1995, Koornneef et al 2002 como somáticos (Garcês et al 2014). El balance entre ABA y niveles de GAs tiene un rol importante en la regulación de la dormancia.…”