YABBY Genes in the Development and Evolution of Land Plants

Abstract

Mounting evidence from genomic and transcriptomic studies suggests that most genetic networks regulating the morphogenesis of land plant sporophytes were co-opted and modified from those already present in streptophyte algae and gametophytes of bryophytes sensu lato. However, thus far, no candidate genes have been identified that could be responsible for “planation”, a conversion from a three-dimensional to a two-dimensional growth pattern. According to the telome theory, “planation” was required for the genesis of the leaf blade in the course of leaf evolution. The key transcription factors responsible for leaf blade development in angiosperms are YABBY proteins, which until recently were thought to be unique for seed plants. Yet, identification of a YABBY homologue in a green alga and the recent findings of YABBY homologues in lycophytes and hornworts suggest that YABBY proteins were already present in the last common ancestor of land plants. Thus, these transcriptional factors could have been involved in “planation”, which fosters our understanding of the origin of leaves. Here, we summarise the current data on functions of YABBY proteins in the vegetative and reproductive development of diverse angiosperms and gymnosperms as well as in the development of lycophytes. Furthermore, we discuss a putative role of YABBY proteins in the genesis of multicellular shoot apical meristems and in the evolution of leaves in early divergent terrestrial plants.

Evolutionary Analysis of the YABBY Gene Family in Brassicaceae

“…The YABBY gene family contains several transcription factor members present in all seed plants [1,2]. The family members have important functions in plant growth and development, such as the polarity establishment in lateral organs, the formation and development of leaves and flowers, and the response to internal plant hormone and external environmental stress signals [3,4]. The family was initially named after the Australian freshwater crayfish following the discovery of the first member, CRABS CLAW, of which the mutation (crc-1) can result in apically unfused carpels in Arabidopsis thaliana [5].…”

Leaf Epidermis: The Ambiguous Symplastic Domain

“…Determination of cell fate and specification of cell layers in SAMs as well as in leaves during their development requires precise regulation of symplastic exchange between cells. A whole orchestra of regulators, such as transcription factors, RNA, and small molecules like hormones move through PD enabling SAM functioning as well as proper development of leaves from leaf primordia (Kitagawa and Jackson, 2017 ; Liu and Chen, 2018 ; Bhatia et al, 2021 ; Maksimova et al, 2021 ; Romanova et al, 2021 ). Moreover, also in the mature leaves, exchange of regulatory molecules as well as assimilates between cells and tissues via PD is a highly important and finely tuned process (Cui et al, 2014 ; Liu and Chen, 2018 ; Dmitrieva et al, 2021 ).…”

Genome-Wide Identification of YABBY Gene Family in Cucurbitaceae and Expression Analysis in Cucumber (Cucumis sativus L.)

“…Based on evolutionary relationships, the angiosperm YABBY genes can be classified into five subfamilies—YAB1, CRC, INO, YAB2, and YAB5 [ 10 , 11 ]. Substantial evidence has demonstrated that the YABBY genes play important roles in many aspects of plant growth and development, such as lateral organ development, establishment of polarity, and reproductive organ development in angiosperms [ 12 , 13 ]. In Arabidopsis, four genes— FIL , YAB2 , YAB3 , and YAB5 —are involved in vegetative tissues development [ 13 , 14 , 15 ].…”

“…Substantial evidence has demonstrated that the YABBY genes play important roles in many aspects of plant growth and development, such as lateral organ development, establishment of polarity, and reproductive organ development in angiosperms [ 12 , 13 ]. In Arabidopsis, four genes— FIL , YAB2 , YAB3 , and YAB5 —are involved in vegetative tissues development [ 13 , 14 , 15 ]. FIL , YAB2 , and YAB3 are specifically expressed in all lateral organ primordia derived from the apical and flower meristems [ 2 , 14 , 16 ].…”