Evolutionary Analysis of the LAFL Genes Involved in the Land Plant Seed Maturation Program

Jing-Dan Han,Gane K.-S Wong,Carl J Rothfels,Chen-Kun Jiang,Guang-Yuan Rao,Xia Li

doi:10.3389/fpls.2017.00439

Abstract

Seeds are one of the most significant innovations in the land plant lineage, critical to the diversification and adaptation of plants to terrestrial environments. From perspective of seed evo-devo, the most crucial developmental stage in this innovation is seed maturation, which includes accumulation of storage reserves, acquisition of desiccation tolerance, and induction of dormancy. Based on previous studies of seed development in the model plant Arabidopsis thaliana, seed maturation is mainly controlled by the LAFL regulatory network, which includes LEAFY COTYLEDON1 (LEC1) and LEC1-LIKE (L1L) of the NF-YB gene family, and ABSCISIC ACID INSENSITIVE3 (ABI3), FUSCA3 (FUS3), and LEC2 (LEAFY COTYLEDON2) of the B3-AFL gene family. In the present study, molecular evolution of these LAFL genes was analyzed, using representative species from across the major plant lineages. Additionally, to elucidate the molecular mechanisms of the seed maturation program, co-expression pattern analyses of LAFL genes were conducted across vascular plants. The results show that the origin of AFL gene family dates back to a common ancestor of bryophytes and vascular plants, while LEC1-type genes are only found in vascular plants. LAFL genes of vascular plants likely specify their co-expression in two different developmental phrases, spore and seed maturation, respectively, and expression patterns vary slightly across the major vascular plants lineages. All the information presented in this study will provide insights into the origin and diversification of seed plants.

Highlights

Seeds, as propagules and dispersal units, play very important roles in the adaptation of seed plants to terrestrial environments (Kenrick and Crane, 1997; Becker and Marin, 2009; Radoeva and Weijers, 2014)
There were studies on the evolution of LEAFY COTYLEDON1 (LEC1)-type genes (Xie et al, 2008), AFL genes (Li et al, 2010; Carbonero et al, 2016), this study presents a comprehensive analysis of LAFL genes by integrating their phylogeny, gene structure, cis-elements and expression patterns together for a better understanding of the evolution of seed maturation programs during plant evolution
According to our extensive phylogenic and gene structure analyses, LEC2 type and ABI3 type genes evolved in a common ancestor of bryophytes and vascular plants, and their gene structure is very conservative

Summary

Introduction

As propagules and dispersal units, play very important roles in the adaptation of seed plants to terrestrial environments (Kenrick and Crane, 1997; Becker and Marin, 2009; Radoeva and Weijers, 2014). Seed maturation, which includes all of the events occurring after cell division has ceased within the embryo (following Harada, 1997), can be considered as a developmental module that is added after embryogenesis It is accomplished with the accumulation of nutrient reserves, the acquisition of desiccation tolerance, the desiccation of seeds, Evolutionary Analysis of LAFL Genes the suppression of precocious germination, and the induction of dormancy (Goldberg et al, 1994; Harada, 1997); these features are each thought to be important in the adaptation of plants to variable and harsh terrestrial environments. The LAFL network represses the expression of genes required for the transition from embryonic to vegetative developments, i.e., the suppression of precocious germination (Giraudat et al, 1992; Nambara et al, 1992; Stone et al, 2001)

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Results

Conclusion