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Abstract

Short brassinosteroid (BR) mutants lk, lka and lkb of
pea (Pisum sativum L.) were investigated by immunofluorescence
microscopy to elucidate the role of
brassinosteroids in cell elongation via an effect on
the microtubules (MTs). This study adds to our
knowledge the fact that brassinolide (BL) can cause
MT realignment in azuki bean and rescue the MT
organization of BR mutants in Arabidopsis. It provides
novel information on both cortical and epidermal
cells and presents detailed information
about the ratios of all MT orientations present,
ranging from transverse (perpendicular to the
elongating axis) to longitudinal (parallel to the
elongating axis). Experiments were conducted in
vivo using intact plants with direct application of a
small amount of brassinolide (BL) to the internode.
Employing a BR-receptor mutant, lka, and the BRsynthesis
mutants, lk and lkb, allowed the identification
and isolation of any BR-induced responses in
the MT cytoskeleton following BL application. Increases
in growth rate were noted in all pea lines
including WT following BL application. These increases
were strong in the BR-synthesis mutants,
but weak in the BR-receptor mutant. Immunofluorescence
revealed significant differences in the
average MT orientation of cortical cells of mutants
versus WTs. Importantly, these mutants possessed
abundant MTs, unlike the BR-deficient bul1-1 mutant
in Arabidopsis. Following BL application, the
epidermal and cortical cells of lk and lkb plants
showed a large and significant shift in MT orientation
towards more transverse, whereas lka plants
showed a small and nonsignificant response in these
cells. These results suggest that the BR response
pathwa

Item Type:	Article
Authors/Creators:	Knowles, CL and Koutoulis, A and Reid, JB
Journal or Publication Title:	Journal of Plant Growth Regulation
ISSN:	0721-7595
DOI / ID Number:	10.1007/s00344-004-0010-x
Additional Information:	The final publication is available at http://www.springerlink.com
Item Statistics:	View statistics for this item

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