BioMEMS for Cell Biology - Introduction to BioMEMS - page 369

(a) (b) (c)

Media + α-factor
+
tracking dye

Inlets

A

Media

B

C

Cell
chamber

Outlet D

E

Tracking dye intensity

(d)

100

80

60

40
20

0

Position in gradient

Wide
Shmoo

Medium
Shmoo

Thin
Shmoo

Clustered Filamentous

FIGURE 6.78 Mating.pheromone.gradient.sensing.in.yeast..(From.Travis.I..Moore,.Ching-Shan.Chou,.
Qing.Nie,.Noo.Li.Jeon,.and.Tau-Mu.Yi,.“Robust.spatial.sensing.of.mating.pheromone.gradients.by.
yeast.cells,”. PLoS ONE .3,.e3865,.2008.)

6.8 Plant Cell Biology
In 1987, practically at the dawn of BioMEMS, a group led by Harvey Hoch at Cornell University
reported what has been, for more than two decades, the only BioMEMS article that deals with
plants. his elegant article used microfabrication to elucidate the role of surface topography in
leaves during fungal infection ( Figure 6.79 ). he spores of the fungi need to ind a pore on the
surface of the leaf, and when they do so, they form an infection structure called an appressorium
that blocks the pore and from which they enter the interior of the leaf ( Figure 6.79a ). How does
the spore ind the pore? Hoch and coworkers built various substrates, some containing a pore
with concentric ridges ( Figure 6.79b ) and some containing parallel ridges of various heights
( Figure 6.79c ), to conclude that spore growth and appressoria formation is stimulated by a par-
ticular range of ridge heights ( Figure 6.79c and d ), which coincides with the ridges observed in
natural leaves.
Recently, Rustem Ismagilov's laboratory at the University of Chicago has built a two-part
microluidic device that allows for inserting plant roots into a microchannel ( Figure 6.80a ). he
microchannel features three inlets so that the roots can be locally perfused with a solution of
choice using heterogeneous laminar low ( Figure 6.80b ). he device was used to demonstrate
the local exposure of live roots of Arabidopsis thaliana (a model organism in plant biology and
genetics, the irst plant genome to be sequenced, and well-suited for light/luorescence micros-
copy because the seedling and the roots are translucent); local exposure to auxin resulted in
local GFP expression in the root and local epidermal hair growth ( Figure 6.80b through d ).