In. Saab et Mm. Sachs, A FLOODING-INDUCED XYLOGLUCAN ENDO-TRANSGLYCOSYLASE HOMOLOG IN MAIZE IS RESPONSIVE TO ETHYLENE AND ASSOCIATED WITH AERENCHYMA, Plant physiology, 112(1), 1996, pp. 385-391
Development of aerenchyma (soft cortical tissue with large intercellul
ar air spaces) in flooded plants results from cell-wall hydrolysis and
eventual cell lysis and is promoted by endogenous ethylene. Despite i
ts adaptive significance, the molecular mechanisms behind aerenchyma d
evelopment remain unknown. We recently isolated a flooding-induced mai
ze (Zea mays L.) gene (wusl1005[gfu]; abbreviated as 1005) encoding a
homolog of xyloglucan endo-transglycosylase (XET), a putative cell-wal
l-loosening enzyme active during germination, expansion, and fruit sof
tening. XET and related enzymes may also be involved in cell-wall meta
bolism during flooding-induced aerenchyma development. Under flooding,
1005 mRNA accumulated in root and mesocotyl locations that subsequent
ly exhibited aerenchyma development and reached maximum levels within
12 h of treatment. Aerenchyma development was observed in the same loc
ations by 48 h of treatment. Treatment with the ethylene synthesis inh
ibitor (aminooxy)acetic acid (AOA), which prevented cortical air space
formation under flooding, almost completely inhibited 1005 mRNA accum
ulation in both organs. AOA treatment had little effect on the accumul
ation of mRNA encoded by adh1, indicating that it did not cause genera
l suppression of flooding-responsive genes. Additionally, ethylene tre
atment under aerobic conditions resulted in aerenchyma development as
well as induction of 1005 in both organs. These results indicate that
1005 is responsive to ethylene. Treatment with anoxia, which suppresse
s ethylene accumulation and aerenchyma development, also resulted in 1
005 induction. However, in contrast to flooding, AOA treatment under a
noxia did not affect 1005 mRNA accumulation, indicating that 1005 is i
nduced via different mechanisms under flooding (hypoxia) and anoxia.