Cuticle formation

piero morandini pm1 at IMIUCCA.CSI.UNIMI.IT
Thu Oct 12 11:26:17 EST 1995


Dear Planted people,
I realised I am probably not the only ignorant about cuticle formation.

I am afraid my main problem remains: how can either the precursors or
the polymerized cutin (the latter being a worse problem than the former)
cross the cell wall and the middle lamella, which are hydrophylic
environments, and still end up as a highly organised hydrophobic
structure.   Anyway, here are the responses I got from the Net.


>Piero:
>I quick check of a few references didn't answer your question but I
>doubt the cutin and wax molecules are assembled extracellularly.  My
>guess is they are secreted via ER ->golgi ->transport vesicles -> cell
>membrane as are the cell wall hemicelluloses.  Thus there is no problem
>of the material passing through a hydrophilic region.  Cellulose is
>thought to be synthesized by enzymes in the cell membrane and released
>outside the cell as it's formed, but I have never heard of such a
>mechanism for cutin and waxes.

>BTY, the 1992 Plant Physiology text by Salisbury and Ross states "Cutins
>and waxes are synthesized by the epidermis and are then somehow secreted
>onto the surface."  Their text is pretty thorough and if a secretion
>mechanism was known when they were writing, they would have included it.


>John Sowell     jsowell at western.edu
>Biology Department
>Western State College
>Gunnsion, CO  81231  USA

*******************************************************

>You might begin by reading Esau, Katherine.  1965.  Plant Anatomy.  2nd Ed
>(or later editions), pp. 155-157.  On page 156 there is a section which
>speaks to your question: "The development of the initial cuticle is
>interpreted as a flooding with a cutin precursor, or procutin (probably
>unsaturated fatty acids, Frey-Wyssling and Muhlethaler, 1959), analogous to
>a drying oil, and a subsequent hardening of this material through
>polymerization under the influence of the air oxygen.  According to a study
>of the cuticle of the apple fruit (Huelin, 1959), however, cutin formation
>is conceived as a process controlled by enzyme action rather than by
>spontaneous oxidation.  The hardening of the cuticle presumably terminates
>further extrusion of wax and cutin precursor and, therefore, these
>substances accumulate beneath the cuticle (Schiefferstein and Loomins,
>1956)."


>Dr. David W. Kramer
>Assistant Professor of Plant Biology
>Ohio State University at Mansfield
>1680 University Drive
>Mansfield, OH  44906
>(419) 755-4344  FAX:  (419) 755-4367
>e-mail:  kramer.8 at osu.edu
-- 

Piero Morandini
Dept. of Biology "L. Gorini" - University of Milan
via Celoria 26
20133  Milan  -  ITALY

Tel:	+39-2-2660-4394  	email:  pm1 at imiucca.csi.unimi.it
Fax:	+39-2-2660-4399



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