TY - JOUR

T1 - The Huperzia selago Shoot Tip Transcriptome Sheds New Light on the Evolution of Leaves

AU - Evkaikina, Anastasiia I.

AU - Berke, Lidija

AU - Romanova, Marina A.

AU - Proux-Wéra, Estelle

AU - Ivanova, Alexandra N.

AU - Rydin, Catarina

AU - Pawlowski, Katharina

AU - Voitsekhovskaja, Olga V.

PY - 2017/9

Y1 - 2017/9

N2 - Lycopodiophyta-consisting of three orders, Lycopodiales, Isoetales and Selaginellales, with different types of shoot apical meristems (SAMs)-form the earliest branch among the extant vascular plants. They represent a sister group to all other vascular plants, from which they differ in that their leaves are microphylls-that is, leaves with a single, unbranched vein, emerging from the protostele without a leaf gap-not megaphylls. All leaves represent determinate organs originating on the flanks of indeterminate SAMs. Thus, leaf formation requires the suppression of indeterminacy, that is, of KNOX transcription factors. In seed plants, this is mediated by different groups of transcription factors including ARP and YABBY. We generated ashoot tip transcriptome of Huperzia selago (Lycopodiales) to examine the genes involved in leaf formation. Our H. Selago transcriptome does not containany ARP homolog, although transcriptomes of Selaginella spp.do. Surprisingly, we discovered a YABBY homolog, although these transcription factors were assumed to have evolved only in seed plants. The existence of a YABBY homolog in H. Selago suggests that YABBY evolved already in the common ancestor of the vascular plants, and subsequently was lost in some lineages like Selaginellales, whereas ARP may have been lost in Lycopodiales. The presence of YABBY in the common ancestor of vascular plants would also support the hypothesis that this common ancestor had a simplex SAM. Furthermore, a comparison of the expression patterns of ARP in shoot tips of Selaginella kraussiana (Harrison CJ, et al. 2005. Independent recruitment of a conserved developmental mechanism during leaf evolution. Nature 434(7032):509-514.) and YABBY in shoot tips of H. Selago implies that the development of micro-phylls, unlike megaphylls, does not seem todepend on the combined activities of ARP and YABBY. Altogether, ourdata show that Lycopodiophyta are a diverse group; so, in order to understand the role of Lycopodiophyta in evolution, representatives of Lycopodiales, Selaginellales, as well as of Isoetales, have to be examined.

AB - Lycopodiophyta-consisting of three orders, Lycopodiales, Isoetales and Selaginellales, with different types of shoot apical meristems (SAMs)-form the earliest branch among the extant vascular plants. They represent a sister group to all other vascular plants, from which they differ in that their leaves are microphylls-that is, leaves with a single, unbranched vein, emerging from the protostele without a leaf gap-not megaphylls. All leaves represent determinate organs originating on the flanks of indeterminate SAMs. Thus, leaf formation requires the suppression of indeterminacy, that is, of KNOX transcription factors. In seed plants, this is mediated by different groups of transcription factors including ARP and YABBY. We generated ashoot tip transcriptome of Huperzia selago (Lycopodiales) to examine the genes involved in leaf formation. Our H. Selago transcriptome does not containany ARP homolog, although transcriptomes of Selaginella spp.do. Surprisingly, we discovered a YABBY homolog, although these transcription factors were assumed to have evolved only in seed plants. The existence of a YABBY homolog in H. Selago suggests that YABBY evolved already in the common ancestor of the vascular plants, and subsequently was lost in some lineages like Selaginellales, whereas ARP may have been lost in Lycopodiales. The presence of YABBY in the common ancestor of vascular plants would also support the hypothesis that this common ancestor had a simplex SAM. Furthermore, a comparison of the expression patterns of ARP in shoot tips of Selaginella kraussiana (Harrison CJ, et al. 2005. Independent recruitment of a conserved developmental mechanism during leaf evolution. Nature 434(7032):509-514.) and YABBY in shoot tips of H. Selago implies that the development of micro-phylls, unlike megaphylls, does not seem todepend on the combined activities of ARP and YABBY. Altogether, ourdata show that Lycopodiophyta are a diverse group; so, in order to understand the role of Lycopodiophyta in evolution, representatives of Lycopodiales, Selaginellales, as well as of Isoetales, have to be examined.

KW - Lycopodiophyta, Huperzia, shoot apex, leaf development, KNOX, ARP, YABBY

UR - http://www.scopus.com/inward/record.url?scp=85044501228&partnerID=8YFLogxK

U2 - doi:10.1093/gbe/evx169

DO - doi:10.1093/gbe/evx169

M3 - Article

C2 - 28957460

AN - SCOPUS:85044501228

VL - 9

SP - 2444

EP - 2460

JO - Genome Biology and Evolution

JF - Genome Biology and Evolution

SN - 1759-6653

IS - 9

ER -