Strigolactone- and Karrikin-Independent SMXL Proteins Are Central Regulators of Phloem Formation

Autor: Gernot Poschet, Rüdiger Hell, Thomas Greb, Eva-Sophie Wallner, Javier Agustí, Vadir López-Salmerón, Iris Sevilem, Ilona Jung, Ivan Lebovka, Yrjö Helariutta, Eija Jokitalo, Karin Grünwald, Ilya Belevich
Přispěvatelé: Helariutta, Yrjo [0000-0002-7287-8459], Apollo - University of Cambridge Repository, University of Helsinki, Institute of Biotechnology, Eija Jokitalo / Principal Investigator, Biosciences, Yrjö Helariutta / Principal Investigator, Plant Biology, Viikki Plant Science Centre (ViPS), Electron Microscopy
Jazyk: angličtina
Předmět:
0106 biological sciences
0301 basic medicine
MAX2
Cell signaling
Protein family
Arabidopsis
Strigolactone
Protein degradation
meristem
01 natural sciences
VASCULAR TISSUE
phloem
General Biochemistry
Genetics and Molecular Biology
Lactones
03 medical and health sciences
Plant Growth Regulators
Gene Expression Regulation
Plant
Report
sieve elements
strigolactone
D53
SHOOT DEVELOPMENT
REQUIRES
biology
Arabidopsis Proteins
fungi
Root meristem growth
food and beverages
REPRESSOR
DEGRADATION
root
biology.organism_classification
karrikin
SMXL
Karrikin
030104 developmental biology
Biochemistry
ARABIDOPSIS-THALIANA
1182 Biochemistry
cell and molecular biology
PROTOPHLOEM DIFFERENTIATION
Phloem
ROOT-MERISTEM GROWTH
General Agricultural and Biological Sciences
SYSTEM
Signal Transduction
RESPONSES
010606 plant biology & botany
Zdroj: Current Biology
ISSN: 0960-9822
DOI: 10.1016/j.cub.2017.03.014
Popis: Summary Plant stem cell niches, the meristems, require long-distance transport of energy metabolites and signaling molecules along the phloem tissue. However, currently it is unclear how specification of phloem cells is controlled. Here we show that the genes SUPPRESSOR OF MAX2 1-LIKE3 (SMXL3), SMXL4, and SMXL5 act as cell-autonomous key regulators of phloem formation in Arabidopsis thaliana. The three genes form an uncharacterized subclade of the SMXL gene family that mediates hormonal strigolactone and karrikin signaling. Strigolactones are endogenous signaling molecules regulating shoot and root branching [1] whereas exogenous karrikin molecules induce germination after wildfires [2]. Both activities depend on the F-box protein and SCF (Skp, Cullin, F-box) complex component MORE AXILLARY GROWTH2 (MAX2) [3, 4, 5]. Strigolactone and karrikin perception leads to MAX2-dependent degradation of distinct SMXL protein family members, which is key for mediating hormonal effects [6, 7, 8, 9, 10, 11, 12]. However, the nature of events immediately downstream of SMXL protein degradation and whether all SMXL proteins mediate strigolactone or karrikin signaling is unknown. In this study we demonstrate that, within the SMXL gene family, specifically SMXL3/4/5 deficiency results in strong defects in phloem formation, altered sugar accumulation, and seedling lethality. By comparing protein stabilities, we show that SMXL3/4/5 proteins function differently to canonical strigolactone and karrikin signaling mediators, although being functionally interchangeable with those under low strigolactone/karrikin signaling conditions. Our observations reveal a fundamental mechanism of phloem formation and indicate that diversity of SMXL protein functions is essential for a steady fuelling of plant meristems.
Highlights • SMXL3/4/5 genes act as general promoters of phloem formation • SMXL3/4/5 proteins are expressed and function very early during phloem development • SMXL3/4/5 proteins do not mediate strigolactone or karrikin signaling • Strigolactone/karrkin-dependent SMXL proteins are able to replace SMXL5
Plants depend on long-distance transport of energy metabolites and signaling molecules along the phloem tissue. Wallner et al. show that phloem formation requires a family of proteins closely related to mediators of a hormonal signalling pathway. An hormone-independent action of the proteins analyzed is essential for robust phloem formation.
Databáze: OpenAIRE
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