Explosive seed dispersal depends on SPL7 to ensure sufficient copper for localized lignin deposition via laccases

Edited by Mary Lou Guerinot, Dartmouth College, Hanover, NH; received February 11, 2022; accepted April 27, 2022
June 6, 2022
119 (24) e2202287119

Significance

The sudden explosion of seed pods in popping cress (Cardamine hirsuta) takes less than 3 ms to accelerate seeds away from the plant. This explosive mechanism relies on polar deposition of the cell-wall polymer lignin. To investigate the genetic basis for polar lignin deposition, we conducted a mutant screen and identified SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 7 (SPL7)—a transcriptional regulator of copper homeostasis. We discovered three multicopper laccases, LAC4, 11, and 17, that precisely colocalize with, and are required for, the polar deposition of lignin in explosive seed pods. Activity of these three laccases depends on SPL7 to acclimate to copper deficiency. Our findings demonstrate how mineral nutrition is integrated with polar lignin deposition to facilitate dispersal.

Abstract

Exploding seed pods evolved in the Arabidopsis relative Cardamine hirsuta via morphomechanical innovations that allow the storage and rapid release of elastic energy. Asymmetric lignin deposition within endocarpb cell walls is one such innovation that is required for explosive seed dispersal and evolved in association with the trait. However, the genetic control of this novel lignin pattern is unknown. Here, we identify three lignin-polymerizing laccases, LAC4, 11, and 17, that precisely colocalize with, and are redundantly required for, asymmetric lignification of endocarpb cells. By screening for C. hirsuta mutants with less lignified fruit valves, we found that loss of function of the transcription factor gene SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 7 (SPL7) caused a reduction in endocarpb cell-wall lignification and a consequent reduction in seed dispersal range. SPL7 is a conserved regulator of copper homeostasis and is both necessary and sufficient for copper to accumulate in the fruit. Laccases are copper-requiring enzymes. We discovered that laccase activity in endocarpb cell walls depends on the SPL7 pathway to acclimate to copper deficiency and provide sufficient copper for lignin polymerization. Hence, SPL7 links mineral nutrition to efficient dispersal of the next generation.

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Data Availability

Short-sequence read data for this study has been deposited in the European Nucleotide Archive (ENA) at the European Molecular Biology Laboratory's European Bioinformatics Institute (EMBL-EBI) under accession number PRJEB50935 (39).
All other study data are included in the article and/or supporting information.

Acknowledgments

We thank P. Huijser, M. Tsiantis, and A. Emonet for comments; K. Lufen for lignin analyses; P. Sarchet for conducting the mutant screen; L. Samuels and C. Kamei for sharing materials; X. Gan for bioinformatic services; A. Stamatakis for greenhouse support; R. Franzen for scanning electron microscopy; and W. Faigl for laccase purification. This work was supported by an International Max Planck Research School studentship (to M.P.-A.), the Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy—EXC 2048/1—Project ID No. 390686111 (to M.P.), and a DFG FOR2581 Plant Morphodynamics grant (to A.H.). Portions of the paper were developed from the thesis of M.P.-A.

Supporting Information

Appendix 01 (PDF)
Dataset S01 (XLSX)

References

1
W. D. Hamilton, R. M. May, Dispersal in stable habitats. Nature 269, 578–581 (1977).
2
H. Kokko, A. López-Sepulcre, From individual dispersal to species ranges: Perspectives for a changing world. Science 313, 789–791 (2006).
3
A. Hay, M. Tsiantis, The genetic basis for differences in leaf form between Arabidopsis thaliana and its wild relative Cardamine hirsuta. Nat. Genet. 38, 942–947 (2006).
4
H. Hofhuis et al., Morphomechanical innovation drives explosive seed dispersal. Cell 166, 222–233 (2016).
5
J. Spence, Y. Vercher, P. Gates, N. Harris, ‘Pod shatter’ in Arabidopsis thaliana, Brassica napus and B. juncea. J. Microsc. 181, 195–203 (1996).
6
R. A. Dixon, J. Barros, Lignin biosynthesis: Old roads revisited and new roads explored. Open Biol. 9, 190215 (2019).
7
Y. Tobimatsu, M. Schuetz, Lignin polymerization: How do plants manage the chemistry so well? Curr. Opin. Biotechnol. 56, 75–81 (2019).
8
M. Schuetz et al., Laccases direct lignification in the discrete secondary cell wall domains of protoxylem. Plant Physiol. 166, 798–807 (2014).
9
S. Naseer et al., Casparian strip diffusion barrier in Arabidopsis is made of a lignin polymer without suberin. Proc. Natl. Acad. Sci. U.S.A. 109, 10101–10106 (2012).
10
N. Hoffmann, A. Benske, H. Betz, M. Schuetz, A. L. Samuels, Laccases and peroxidases co-localize in lignified secondary cell walls throughout stem development. Plant Physiol. 184, 806–822 (2020).
11
E. Yi Chou et al., Distribution, mobility, and anchoring of lignin-related oxidative enzymes in Arabidopsis secondary cell walls. J. Exp. Bot. 69, 1849–1859 (2018).
12
Y. Lee, M. C. Rubio, J. Alassimone, N. Geldner, A mechanism for localized lignin deposition in the endodermis. Cell 153, 402–412 (2013).
13
B. C. McCaig, R. B. Meagher, J. F. Dean, Gene structure and molecular analysis of the laccase-like multicopper oxidase (LMCO) gene family in Arabidopsis thaliana. Planta 221, 619–636 (2005).
14
M. Tognolli, C. Penel, H. Greppin, P. Simon, Analysis and expression of the class III peroxidase large gene family in Arabidopsis thaliana. Gene 288, 129–138 (2002).
15
K. G. Welinder et al., Structural diversity and transcription of class III peroxidases from Arabidopsis thaliana. Eur. J. Biochem. 269, 6063–6081 (2002).
16
N. Rojas-Murcia et al., High-order mutants reveal an essential requirement for peroxidases but not laccases in Casparian strip lignification. Proc. Natl. Acad. Sci. U.S.A. 117, 29166–29177 (2020).
17
S. Berthet et al., Disruption of LACCASE4 and 17 results in tissue-specific alterations to lignification of Arabidopsis thaliana stems. Plant Cell 23, 1124–1137 (2011).
18
Q. Zhao et al., Laccase is necessary and nonredundant with peroxidase for lignin polymerization during vascular development in Arabidopsis. Plant Cell 25, 3976–3987 (2013).
19
J. Barros, H. Serk, I. Granlund, E. Pesquet, The cell biology of lignification in higher plants. Ann. Bot. 115, 1053–1074 (2015).
20
J. Wang et al., Lignin engineering through laccase modification: A promising field for energy plant improvement. Biotechnol. Biofuels 8, 145 (2015).
21
B. Printz, S. Lutts, J. F. Hausman, K. Sergeant, Copper trafficking in plants and its implication on cell wall dynamics. Front. Plant Sci. 7, 601 (2016).
22
J. L. Burkhead, K. A. Gogolin Reynolds, S. E. Abdel-Ghany, C. M. Cohu, M. Pilon, Copper homeostasis. New Phytol. 182, 799–816 (2009).
23
R. P. Birkenbihl, G. Jach, H. Saedler, P. Huijser, Functional dissection of the plant-specific SBP-domain: Overlap of the DNA-binding and nuclear localization domains. J. Mol. Biol. 352, 585–596 (2005).
24
P. Huijser, M. Schmid, The control of developmental phase transitions in plants. Development 138, 4117–4129 (2011).
25
J. M. Quinn, S. Merchant, Two copper-responsive elements associated with the Chlamydomonas Cyc6 gene function as targets for transcriptional activators. Plant Cell 7, 623–628 (1995).
26
J. Kropat et al., A regulator of nutritional copper signaling in Chlamydomonas is an SBP domain protein that recognizes the GTAC core of copper response element. Proc. Natl. Acad. Sci. U.S.A. 102, 18730–18735 (2005).
27
M. Bernal et al., Transcriptome sequencing identifies SPL7-regulated copper acquisition genes FRO4/FRO5 and the copper dependence of iron homeostasis in Arabidopsis. Plant Cell 24, 738–761 (2012).
28
S. E. Abdel-Ghany, M. Pilon, MicroRNA-mediated systemic down-regulation of copper protein expression in response to low copper availability in Arabidopsis. J. Biol. Chem. 283, 15932–15945 (2008).
29
H. Yamasaki, M. Hayashi, M. Fukazawa, Y. Kobayashi, T. Shikanai, SQUAMOSA promoter binding protein-like7 is a central regulator for copper homeostasis in Arabidopsis. Plant Cell 21, 347–361 (2009).
30
M. Weigel et al., Plastocyanin is indispensable for photosynthetic electron flow in Arabidopsis thaliana. J. Biol. Chem. 278, 31286–31289 (2003).
31
A. Garcia-Molina, S. Xing, P. Huijser, Functional characterisation of Arabidopsis SPL7 conserved protein domains suggests novel regulatory mechanisms in the Cu deficiency response. BMC Plant Biol. 14, 231 (2014).
32
M. Rahmati Ishka, O. K. Vatamaniuk, Copper deficiency alters shoot architecture and reduces fertility of both gynoecium and androecium in Arabidopsis thaliana. Plant Direct 4, e00288 (2020).
33
J. Yan et al., Arabidopsis pollen fertility requires the transcription factors CITF1 and SPL7 that regulate copper delivery to anthers and jasmonic acid synthesis. Plant Cell 29, 3012–3029 (2017).
34
X. Gan et al., The Cardamine hirsuta genome offers insight into the evolution of morphological diversity. Nat. Plants 2, 16167 (2016).
35
Y. Lee et al., A lignin molecular brace controls precision processing of cell walls critical for surface integrity in Arabidopsis. Cell 173, 1468–1480.e9 (2018).
36
N. Hoffmann, S. King, A. L. Samuels, H. E. McFarlane, Subcellular coordination of plant cell wall synthesis. Dev. Cell 56, 933–948 (2021).
37
R. Ursache, T. G. Andersen, P. Marhavý, N. Geldner, A protocol for combining fluorescent proteins with histological stains for diverse cell wall components. Plant J. 93, 399–412 (2018).
38
C. E. Foster, T. M. Martin, M. Pauly, Comprehensive compositional analysis of plant cell walls (lignocellulosic biomass) part I: Lignin. J. Vis. Exp. (37), 1745 (2010).
39
M. Pérez-Antón, A. Hay, Project: PRJEB50935. European Nucleotide Archive. https://www.ebi.ac.uk/ena/browser/view/PRJEB50935. Deposited 15 April 2022.
40
S. Anders, W. Huber, Differential expression analysis for sequence count data. Genome Biol. 11, R106 (2010).
41
R Core Team, R: A Language and Environment for Statistical Computing (R Foundation for Statistical Computing, Vienna, Austria, 2019).

Information & Authors

Information

Published in

Go to Proceedings of the National Academy of Sciences
Go to Proceedings of the National Academy of Sciences
Proceedings of the National Academy of Sciences
Vol. 119 | No. 24
June 14, 2022
PubMed: 35666865

Classifications

Data Availability

Short-sequence read data for this study has been deposited in the European Nucleotide Archive (ENA) at the European Molecular Biology Laboratory's European Bioinformatics Institute (EMBL-EBI) under accession number PRJEB50935 (39).
All other study data are included in the article and/or supporting information.

Submission history

Received: February 11, 2022
Accepted: April 27, 2022
Published online: June 6, 2022
Published in issue: June 14, 2022

Keywords

  1. Cardamine hirsuta
  2. lignin
  3. laccases
  4. squamosa promoter-binding protein-like 7
  5. seed dispersal

Acknowledgments

We thank P. Huijser, M. Tsiantis, and A. Emonet for comments; K. Lufen for lignin analyses; P. Sarchet for conducting the mutant screen; L. Samuels and C. Kamei for sharing materials; X. Gan for bioinformatic services; A. Stamatakis for greenhouse support; R. Franzen for scanning electron microscopy; and W. Faigl for laccase purification. This work was supported by an International Max Planck Research School studentship (to M.P.-A.), the Deutsche Forschungsgemeinschaft (DFG) under Germany’s Excellence Strategy—EXC 2048/1—Project ID No. 390686111 (to M.P.), and a DFG FOR2581 Plant Morphodynamics grant (to A.H.). Portions of the paper were developed from the thesis of M.P.-A.

Notes

This article is a PNAS Direct Submission.

Authors

Affiliations

Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
Present address: Institute of Anatomy, University of Cologne, 50931 Cologne, Germany.
Hugo Hofhuis
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany
Present address: KeyGene N.V., 6700 AE Wageningen, The Netherlands.
Cologne Biocenter, University of Cologne, 50674 Cologne, Germany
Institute for Plant Cell Biology and Biotechnology, Heinrich-Heine University Düsseldorf, 40225 Düsseldorf, Germany
Department of Comparative Development and Genetics, Max Planck Institute for Plant Breeding Research, 50829 Cologne, Germany

Notes

3
To whom correspondence may be addressed. Email: [email protected].
Author contributions: M.P.-A. and A.H. designed research; M.P.-A., I.S., P.K., and H.H. performed research; S.M. and M.P. contributed new reagents/analytic tools; M.P.-A. analyzed data; and M.P.-A. and A.H. wrote the paper.

Competing Interests

The authors declare no competing interest.

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    Explosive seed dispersal depends on SPL7 to ensure sufficient copper for localized lignin deposition via laccases
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