Enhanced cell expansion in a KRP2 overexpressor is mediated by increased V-ATPase activity.
Decreased cell numbers during leaf development often trigger increased cell size, a phenomenon called compensation. In compensation-exhibiting mutants, the unusually high cell expansion activity occurs through two different mechanisms during the post-mitotic stage of leaf development, except in the KIP-RELATED PROTEIN 2-overexpressing line (KRP2 o/e), whose cell sizes are 2-fold greater during proliferative growth. However, the molecular basis of compensated cell expansion (CCE) has not been characterized. The det3-1 mutant has a mutation in the C-subunit of the vacuolar-type H(+)-ATPase (V-ATPase) complex that causes a 50% decrease in its activity and cell size. To determine the contribution of V-ATPase activity to CCE, the cellular phenotypes of double mutants between det3-1 and compensation-exhibiting fugu5-1, an3-4, fas1-5 and KRP2 o/e were analyzed in detail. Interestingly, while decreased V-ATPase activity caused by det3-1 did not suppress CCE in fugu5-1, fas1-5 and an3-4, CCE in KRP2 o/e was totally suppressed. Furthermore, measurements revealed that the activity and quantity of the A-subunit of the V-ATPase complex were significantly increased in the shoots of KRP2 o/e plants. Importantly, the unusually increased size of actively dividing KRP2 o/e cells was restored to normal in the det3-1 background. Taken together, our data strongly suggest that CCE in KRP2 o/e, but not in other compensation-exhibiting mutants, occurs exclusively through the increase of V-ATPase activity.
Department of Biology, Tokyo Gakugei University, Koganei-shi, 184-8501 Japan.
Ali
A
Ferjani
Kazuki
K
Ishikawa
Mariko
M
Asaoka
Masanori
M
Ishida
Gorou
G
Horiguchi
Masayoshi
M
Maeshima
Hirokazu
H
Tsukaya
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D030821:Plants, Genetically Modified / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D018797:Cell Cycle Proteins; C407546:ICK2 protein, Arabidopsis; D000251:Adenosine Triphosphatases
Arabidopsis; Cell size; Compensation; KRP2; Leaf development; V-ATPase