Biology Reference
In-Depth Information
First,
Arabidopsis
has multiple types of nectaries (Davis et al., 1998),
while tobacco has a single, large nectary at the base of the gynoecium
(
Carter
et al.,
1999
). Second, the tobacco nectary is 500-fold larger than the
nectaries of
Arabidopsis
, which means that we can readily isolate sufficient
quantities of material for cloning, microscopy, and biochemical analyses.
Third, a single
Arabidopsis
bolt typically produces less than 20 flowers at a
time. Our tobacco line is indeterminate, continuously producing large num-
bers (up to 150) of flowers. Consequently, we can isolate large quantities
of materials for bioanalysis, including hundreds of millilitres of tobacco
nectar and tens of grams of nectary tissue at any desired developmental
stage. Finally, Mysore et al. (2001) have proposed that there is much to be
learned regarding general angiosperm genetics by a more broad-based app-
roach investigating a number of plant species, rather than a strict reliance
on the
Arabidopsis
genome. Thus, we believe that analysis of nectary func-
tion in ornamental tobacco nectaries can serve as a general model for nectary
function among a large proportion of the angiosperms and can enlarge our
global understanding of plant genomics, particularly with regard to this
unique floral organ.
We have therefore worked exclusively with a diploid ornamental tobacco
line (LxS8). This line was derived from an interspecific cross of
Nicotiana
langsdorffii
×
N. sanderae
(Kornaga, 1993; Kornaga et al., 1997). This line
produces extraordinary levels of nectar, much higher than either of its parents.
It is both male and female fertile, but is largely self-incompatible. It does,
however, set high levels of seed when cross-pollinated. We routinely propa-
gate it clonally to produce large numbers of identical plants. We have also
developed methods for transformation of this line of tobacco.
Figure 1.
Tobacco nectary developmental stages. The nectary is located at the base of the
gynoecium. Stage 2 (early filling), stage 6 (filling/beginning ripening), stage 12 (mature, at
anthesis)
