THE BLUE LIGHT-RESPONSIVE ATHH2 GENE OF ARABIDOPSIS-THALIANA IS PRIMARILY EXPRESSED IN EXPANDING AS WELL AS IN DIFFERENTIATING CELLS AND ENCODES A PUTATIVE CHANNEL PROTEIN OF THE PLASMALEMMA
R. Kaldenhoff et al., THE BLUE LIGHT-RESPONSIVE ATHH2 GENE OF ARABIDOPSIS-THALIANA IS PRIMARILY EXPRESSED IN EXPANDING AS WELL AS IN DIFFERENTIATING CELLS AND ENCODES A PUTATIVE CHANNEL PROTEIN OF THE PLASMALEMMA, Plant journal, 7(1), 1995, pp. 87-95
According to our previous studies the Arabidopsis gene AthH2 which is
inducible by blue light and phytohormones codes for an intrinsic membr
ane protein. It bears a resemblance to several distinct channel protei
ns of plant and animal species classified as the MIP/NOD-26/GlpF famil
y. In the present study biochemical analyses and electron microscopic
immunochemistry were used to elucidate the subcellular location of the
AthH2 protein. The results clearly demonstrate that it is an exclusiv
e constituent of the plasmalemma. Furthermore, the expression of the A
thH2 gene in transgenic Arabidopsis plants containing the promoter reg
ion of AthH2 fused to the beta-glucuronidase (gus) reporter gene was s
tudied. The in situ localization of gus activity revealed that the spe
cific promoter is temporally activated by light in expanding and/or di
fferentiating cells comprising newly formed tissues and organs: root e
longation zone, guard cells of stomata, vascular bundle sheaths, filam
ents of stamen and young siliques. Several sites of gus expression coi
ncide spatially with those of in situ hybridization and the immunocyto
chemical reaction, respectively, suggesting that the AthH2 promoter ha
d correctly responded to light as an important exogenous factor with r
elevance to the complex pattern of differentiation. Studies with proto
plasts from plants transformed with an antisense construct revealed a
water transport capacity of the AthH2 protein.