Plant Tracheary Elements


The plant tracheary element is the constituent of vessels and tracheids. Tracheary elements are characterised by patterned secondary wall thickenings and programmed cell death (PCD) at maturity. Their differentiation is induced by plant hormones such as auxin, cytokinin and brassinosteroids, and suppressed by a small peptide, tracheary element differentiation inhibitory factor (TDIF), secreted from phloem cells. The final determination of tracheary element differentiation is initiated by master transcription factors, VAD6 and VND7 (vascular‐related NAC‐domain 7). The secondary wall pattern is formed by guiding the movement of cellulose synthase complex in the plasma membrane by the cortical microtubules. The PCD during tracheary element differentiation is initiated by the rupture of the central vacuole in which cell death‐related hydrolytic enzymes have been accumulated. Thus the process of tracheary element differentiation is well understood, so that tracheary element differentiation is an excellent model of cell differentiation in plants.

Key Concepts:

  • The xylem, which is tissue specific to the vascular plants, is composed of tracheary elements (TEs), parenchyma cells and fibres.

  • Procambial cells produce the primary xylem containing protoxylem and metaxylem TEs in planta.

  • Typical characteristics of TEs are patterned secondary wall thickenings and programmed cell death (PCD).

  • TE differentiation is regulated by plant hormones such as auxin, cytokinin and brassinosteroids.

  • A small peptide secreted from phloem cells prevents procambial cells from differentiating into TEs.

  • VND6 and VND7 are master transcription factors that initiate TE differentiation.

  • Microtubules determine the secondary wall pattern by guiding the movement of cellulose synthase complex in the plasma membrane.

  • During the formation of secondary walls, levels of cellulose and hemicellulose increase and the deposition of pectin ceases, and a little later lignin deposition starts.

  • The central vacuole plays a crucial role in TE PCD.

  • A Zinnia xylogenic culture is an excellent model system of TE differentiation.

Keywords: auxin; brassinosteroids; cell communication; cytokinin; master transcription factors; procambium; programmed cell death; secondary cell walls; xylem; Zinnia

Figure 1.

A single TE that is being differentiated from a single Zinnia mesophyll cell.

Figure 2.

TEs formed ectopically in epidermal tissue by over‐expression of VND7. This picture is taken by M Yamaguchi and T Demura.

Figure 3.

An illustration showing that cortical microtubules control the position and orientation of secondary wall thickenings. This is drawn by Y Oda.

Figure 4.

The process of TE differentiation in the Zinnia xylogenic culture. The initiation of differentiation occurs by a combination of auxin and cytokinin. The process of the in vitro TE differentiation is divided into three stages.



Baima S, Possenti M, Matteucci A et al. (2001) The Arabidopsis ATHB‐8 HD‐zip protein acts as a differentiation‐promoting transcription factor of the vascular meristems. Plant Physiology 126: 643–655.

Boerjan W, Ralph J and Baucher M (2003) Lignin biosynthesis. Annual Review of Plant Biology 54: 519–546.

Bowman J (1993) Arabidopsis. New York: Springer.

Demura T and Fukuda H (2007) Transcriptional regulation in wood formation. Trends in Plant Science 12: 64–70.

Demura T, Tashiro G, Horiguchi G et al. (2002) Visualization by comprehensive microarray analysis of gene expression programs during transdifferentiation of mesophyll cells into xylem cells. Proceedings of the National Academy of Sciences of the USA 99: 15794–15799.

Doblin M S, Kurek I, Jacob‐Wilk D and Delmer DP (2002) Cellulose biosynthesis in plants: from genes to rosettes. Plant & Cell Physiology 43: 1407–1420.

Fukuda H (1997) Tracheary element differentiation. Plant Cell 9: 1147–1156.

Fukuda H and Komamine A (1980) Establishment of an experimental system for the tracheary element differentiation from single cells isolated from the mesophyll of Zinnia elegans. Plant Physiology 65: 57–60.

Fukuda H and Komamine A (1985) Cytodifferentiation. In: IK Vasil (ed.) Cell Culture and Somatic Cell Genetics of Plants, pp. 149–212. New York: Academic Press Inc.

Funk V, Kositsup B, Zhao C and Beers EP (2002) The Arabidopsis xylem peptidase XCP1 is a tracheary element vacuolar protein that may be a papain ortholog. Plant Physiology 128: 84–94.

Hirakawa Y, Shinohara H, Kondo Y et al. (2008) Non‐cell‐autonomous control of vascular stem cell fates by a CLE peptide/receptor system. Proceedings of the National Academy of Sciences of the USA 105: 15208.

Ito J and Fukuda H (2002) ZEN1 is a key enzyme in degradation of nuclear DNA during programmed cell death of tracheary elements. Plant Cell 14: 3201–3211.

Ito Y, Nakanomyo I, Motose H et al. (2006) Dodeca‐CLE peptides as suppressors of plant stem cell differentiation. Science 313: 842–845.

Ito‐Ohashi K and Fukuda H (2003) HD‐zip III homeobox genes that include a novel member, ZeHB‐13 (Zinnia)/ATHB‐15 (Arabidopsis), are involved in procambium and xylem cell differentiation. Plant & Cell Physiology 44: 1350–1358.

Kobayashi H, Fukuda H and Shibaoka H (1988) Interrelationship between the spatial disposition of actin filaments and microtubules during the differentiation of tracheary elements in cultured Zinnia cells. Protoplasma 143: 29–37.

Kubo M, Udagawa M, Nishikubo N et al. (2005) Transcription switches for protoxylem and metaxylem vessel formation. Genes & Development 19: 1855–1860.

Kuriyama H and Fukuda H (2002) Developmental programmed cell death in plants. Current Opinion in Plant Biology 5: 568–573.

Mähönen AP, Bishopp A, Higuchi M et al. (2006) Cytokinin signaling and its inhibitor AHP6 regulate cell fate during vascular development. Science 311: 94–98.

Mähönen AP, Bonke M, Kauppinen L et al. (2000) A novel two‐component hybrid molecule regulates vascular morphogenesis of the Arabidopsis root. Genes & Development 14: 2938–2943.

McCarthy RL, Zhong R and Ye ZH (2009) MYB83 is a direct target of SND1 and acts redundantly with MYB46 in the regulation of secondary cell wall biosynthesis in Arabidopsis. Plant & Cell Physiology 50: 1950–1964.

McConnell JR, Emery J, Eshed Y et al. (2001) Role of PHABULOSA and PHAVOLUTA in determining radial patterning in shoots. Nature 411: 709–713.

Milioni D, Sado PE, Stacey NJ, Roberts K and McCann MC (2002) Early gene expression associated with the commitment and differentiation of a plant tracheary element is revealed by cDNA‐amplified fragment length polymorphism analysis. Plant Cell 14: 2813–2824.

Mitsuda N, Seki M, Shinozaki K and Ohme‐Takagi M (2005) The NAC transcription factors NST1 and NST2 of Arabidopsis regulate secondary wall thickenings and are required for anther dehiscence. Plant Cell 17: 2993–3006.

Motose H, Sugiyama M and Fukuda H (2004) A proteoglycan mediates inductive interaction during plant vascular development. Nature 429: 873–878.

Obara K, Kuriyama H and Fukuda H (2001) Direct evidence of active and rapid nuclear degradation triggered by vacuole rupture during programmed cell death in Zinnia. Plant Physiology 125: 615–626.

Oda Y, Mimura T and Hasezawa S (2005) Regulation of secondary cell wall development by cortical microtubules during tracheary element differentiation in Arabidopsis cell suspensions. Plant Physiology 137: 1027–1036.

Ohashi‐Ito K, Demura T and Fukuda H (2005) Class III homeodomain leucine‐zipper proteins regulate xylem cell differentiation. Plant & Cell Physiology 46: 1646–1656.

Sachs T (1981) The control of the patterned differentiation of vascular tissues. Advances in Botanical Research 9: 151–262.

Taylor NG, Howells RM, Huttly AK, Vickers K and Turner SR (2003) Interactions among three distinct CesA proteins essential for cellulose synthesis. Proceedings of the National Academy of Sciences of the USA 100: 1450–1455.

Torrey JG, Fosket DE and Hepler PK (1971) Xylem formation: a paradigm of cytodifferentiation in higher plants. American Scientist 59: 338–352.

Yamamoto R, Demura T and Fukuda H (1997) Brassinosteroids induce entry into the final stage of tracheary element differentiation in cultured Zinnia cells. Plant & Cell Physiology 38: 980–983.

Yamamoto R, Fujioka S, Demura T et al. (2001) Brassinosteroid levels increase drastically prior to morphogenesis of tracheary elements. Plant Physiology 125: 556–563.

York WS and O'Neill MA (2008) Biochemical control of xylan biosynthesis – which end is up? Current Opinion in Plant Biology 11: 258–265.

Yoshida S, Iwamoto K, Demura T and Fukuda H (2009) Comprehensive analysis of the regulatory roles of auxin in early transdifferentiation into xylem cells. Plant Molecular Biology 70: 457–469.

Yoshimura T, Demura T, Igarashi M and Fukuda H (1996) Differential expression of three genes for different β‐tubulin isoforms during the initial culture of Zinnia mesophyll cells that divide and differentiate into tracheary elements. Plant & Cell Physiology 37: 1167–1176.

Zhong R and Ye Z (2007) Regulation of cell wall biosynthesis. Current Opinion in Plant Biology 10: 564–572.

Zhou J, Lee C, Zhong R and Ye Z‐H (2009) MYB58 and MYB63 are transcriptional activators of the lignin biosynthetic pathway during secondary cell wall formation in Arabidopsis. Plant Cell 21: 248–266.

Further Reading

Aloni R (1987) Differentiation of vascular tissues. Annual Review of Plant Physiology 38: 179–204.

Fukuda H (2004) Signals that govern plant vascular cell differentiation. Nature Reviews. Molecular Cell Biology 5: 379–391.

Roberts LW, Gahan PB and Aloni R (1988) Vascular Differentiation and Plant Growth Regulators. Berlin: Springer.

Turner S, Gallois P and Brown D (2007) Tracheary element differentiation. Annual Review of Plant Biology 58: 407–433.

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Fukuda, Hiroo(Sep 2010) Plant Tracheary Elements. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0001814.pub2]