1. Plant Growth
Size & shape depends on cell # & cell size
Decide when,where and which way to divide

2. Plant Growth
Decide which way to divide & which way to elongate
Periclinal = perpendicular to surface: get longer
Anticlinal = parallel to surface: add more layers
Now must decide which way to elongate: which walls to stretch

3. Plant Cell Walls and Growth
Carbohydrate barrier
surrounding cell
Protects & gives cell shape
1˚ wall made first
mainly cellulose
Can stretch!
2˚ wall made after growth
stops
Lignins make it tough

4. Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
6 CES enzymes form a “rosette”: each makes 6 chains -> 36/fiber
Rosettes are guided
by microtubules

5. Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
6 CES enzymes form a “rosette”: each makes 6 chains
Rosettes are guided by microtubules
Deposition pattern determines direction of elongation

6. Plant Cell Walls and Growth
Cellulose pattern is tightly controlled
Deposition pattern determines direction of elongation
New fibers are perpendicular to growth direction, yet fibers form a mesh

7. Plant Cell Walls and Growth
New fibers are perpendicular to growth direction, yet fibers form a mesh
Multinet hypothesis: fibers reorient as cell elongates
Old fibers are anchored so gradually shift as cell grows
Result = mesh

8. Plant Cell Walls and Growth
1˚ walls = 25% cellulose, 25% hemicellulose, 35% pectin, 5% protein (but highly variable)
Hemicelluloses AKA cross-linking glycans: bind cellulose

9. Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans: bind cellulose
Coat cellulose & bind
neighbor

10. Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans
Coat cellulose & bind neighbor
Diverse group of glucans: also linked b 1-4, but may have other sugars and components attached to C6

11. Plant Cell Walls and Growth
Hemicelluloses AKA cross-linking glycans
A diverse group of glucans also linked b 1-4, but may have other sugars and components attached to C6
makes digestion more difficult
Assembled in Golgi
Secreted cf woven

12. Pectins: fill space between cellulose-hemicellulose fibers
Form gel that determines cell wall porosity (& makes jam)
Acidic, so also modulate pH & bind polars
See distinct types of pectins deposited at specific locations at cell corners

13. Pectins
Pectins: fill space between cellulose-hemicellulose fibers
Form gel that determines cell wall porosity (& makes jam)
Acidic, so also modulate pH & bind polars
Backbone is 1-4 linked galacturonic acid

14. Pectins
Backbone is 1-4 linked galacturonic acid
Have complex sugar side-chains, vary by spp.

15. Pectins
Backbone is 1-4 linked galacturonic acid
Have complex sugar side-chains, vary by spp.

16. Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins

17. Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins
Amounts vary between cell types & conditions

18. Plant Cell Walls and Growth
Also 4 main multigenic families of structural proteins
Amounts vary between cell types & conditions
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
Proline changed to hydroxyproline in Golgi

19. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
Proline changed to hydroxyproline in Golgi
Highly glycosylated: helps bind CH2O

20. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
Proline changed to hydroxyproline in Golgi
Highly glycosylated: helps bind CH2O
Common in cambium, phloem

21. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
Proline changed to hydroxyproline in Golgi
Highly glycosylated: helps bind CH2O
Common in cambium, phloem
Help lock the wall after growth ceases

22. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
Proline changed to hydroxyproline in Golgi
Highly glycosylated: helps bind CH2O
Common in cambium, phloem
Help lock the wall after growth ceases
Induced by wounding
2. PRP: proline-rich proteins

23. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O

24. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O
Common in xylem, fibers, cortex

25. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O
Common in xylem, fibers, cortex
May help lock HRGPs together

26. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O
Common in xylem, fibers, cortex
May help lock HRGPs together
GRP: Glycine-rich proteins
No glycosylation = little interaction with CH2O

27. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O
Common in xylem, fibers, cortex
May help lock HRGPs together
GRP: Glycine-rich proteins
No glycosylation = little interaction with CH2O
Common in xylem

28. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
Low glycosylation = little interaction with CH2O
Common in xylem, fibers, cortex
May help lock HRGPs together
GRP: Glycine-rich proteins
No glycosylation = little interaction with CH2O
Common in xylem
May help lock HRGPs & PRPs together

29. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
3. GRP: Glycine-rich proteins
No glycosylation = little interaction with CH2O
Common in xylem
May help lock HRGPs & PRPs together
4. Arabinogalactan proteins

30. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
3. GRP: Glycine-rich proteins
4. Arabinogalactan proteins
Highly glycosylated: helps bind CH2O

31. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
3. GRP: Glycine-rich proteins
4. Arabinogalactan proteins
Highly glycosylated: helps bind CH2O
Anchored to PM by GPI

32. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
3. GRP: Glycine-rich proteins
4. Arabinogalactan proteins
Highly glycosylated: helps bind CH2O
Anchored to PM by GPI
Help cell adhesion and cell signaling

33. Plant Cell Wall Proteins
HRGP: hydroxyproline-rich glycoproteins (eg extensin)
PRP: proline-rich proteins
3. GRP: Glycine-rich proteins
4. Arabinogalactan proteins
Highly glycosylated: helps bind CH2O
Anchored to PM by GPI
Help cell adhesion and cell signaling
5. Also many enzymes involved in cell wall synthesis and loosening