Nitric oxide is involved in the regulation of guard mother cell division
by inhibiting the synthesis of ACC
A stoma forms by a series of asymmetric divisions of a stomatal lineage
precursor cell and the terminal division of a guard mother cell (GMC).
The symmetric division of the GMC is rigidly restricted to only once
through complex genetic regulation mechanisms. Here, we show that nitric
oxide (NO) is involved in the regulation of the GMC terminal division.
NO donor treatment results in the formation of single guard cells
(SGCs). SGCs are also produced in plants that accumulate high NO,
whereas clustered guard cells (GCs) appear in plants with low NO
accumulation. NO treatment promotes the formation of SGCs in the
stomatal cell signaling mutants sdd1, epf1 epf2, tmm1,
erl2 and yda-1, reduces the cell number per stomatal
cluster in the fama-1 and flp-1 myb88, but has no effect
on stomatal cells of cdkb1;1 cyca2;2 cyca2;3 cyca2;4 quadruple
mutants. Aminocyclopropane-1-carboxylic acid (ACC), a positive regulator
of GMC division, reduces the NO-induced SGC formation. Further
investigation found that NO inhibits ACC synthesis by repressing the
expression of several ACC SYNTHASE ( ACS) genes, and in
turn ACC represses NO accumulation by promoting the expression of
HEMOGLOBIN 1 ( HB1) which encodes a NO scavenger. This
work shows that NO plays a role in the regulation of the GMC terminal
division by modulating ACC accumulation in the Arabidopsis cotyledon.