Plant Development

How does plant development differ from animal development?

Where do the various parts of a plant come from?

= hemicellulose

Plant Cell Wall

Cellulose microfibrils in cell wall

Microtubules beneath plasma membrane

Cellulose microfibril synthesis

Cellulose microfibrils of primary cell wall

Plant cell expansion:Loosen wall in a particular dimensionDrive expansion with turgor pressure

Secondary walls have more layers of polysaccharides, lignin cross-linking.A thicker wall cannot stretch.

Zhong and Ye (2007) Current Opinion in Plant Biology 10: 564-572

Arabidopsis embryo development inside the seed

Embryo fate map

Vegetative Shoot apical meristem (SAM)

Vegetative shoot apical meristem (SAM)

Bushy mutants of pea

Morris et al. (2001) Plant Physiology 126: 1205-1213

Umehara et al. (2008) Nature 455, 195-200

Mutants define the strigolactone biosynthetic pathway in Arabidopsis, pea, and rice

Synthesis

Response

Umehara et al. (2008) Nature 455, 195-200

GR24 inhibits bud outgrowth in strigolactone-deficient mutants

Rice Arabidopsis

Model for mechanism of apical dominance

Shoot apical meristem, leaf primordia

Root, Stem

Lateral bud

Strigolactonetransport

Auxin transport

Auxintransport(PIN proteins)

Strigolactone inhibits transport from lateral bud

Bud grows if it can export auxin

Root meristem

Confocal microscope image of Arabidopsis root

Cyclin::GFP

Which cells are the stem cells?

Which cells are the stem cells?

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0d 1d 3d 5d

Effect of ablation of quiescent center (QC) on tissue-specific marker gene expression

(from Sabatini et al., 1999, Cell 99: 463-472)

The Quiescent Center is the stem cell niche

Whole embryos can self-organize from somatic cells

Friday, April 9th – Class will be in 101 Greenlaw

Regulatory function of Rb protein

Wild type Rb-related RNAi silenced

Silencing Rb-related gene results in extra stem cells

Wildwater et al. (2005) Cell 123: 1337-1349

(Brown marks starch in differentiated root cap cells.)

Control Ectopic Rb-related expression

Ectopic expression of Rb-related gene results in loss of stem cells

Wildwater et al. (2005) Cell 123: 1337-1349

(slight overexpression)

(strong overexpression)