Presentacion

[Plant Signaling & Behavior 3:3, 202-203; March 2008]; ©2008 Landes Bioscience

Article Addendum

Low temperature acclimation mediated by ethanol production is essential for chilling tolerance in rice roots
Hisashi Kato‑Noguchi
Department of Applied Biological Science; Faculty of Agriculture; Kagawa University; Miki, Kagawa, Japan

Abbreviations: ADH, alcohol dehydrogenase; LP-PT, lowtemperature pretreatment; HSP, heat shock protein Key words: acclimation, alcohol dehydrogenase, chilling tolerance, ethanol, heat shock protein, low temperature, Oryza sativa

Rice seedlings (Oryza sativa L.) were subjected to low tempera‑ ture pretreatment (LT‑PT; 10˚C) for various length of time followed by a 48‑h chilling temperature stress (2˚C). Chilling tolerance of rice roots was improvedwith increasing duration of LT‑PT, but HT‑PT longer than 12 h gave no additional improve‑ ment. LT‑PT did not change in fatty acid composition in rice roots under the present experimental condition. Alcohol dehydro‑ genase (ADH) activity and ethanol concentration in the roots were increased with increasing duration of LT‑PT up to 12 h, which indicates that LT‑PT increased ethanol fermentation inthe roots. 4‑Methylpyrazole, a potent inhibitor of ADH, reduced the ethanol concentration and the chilling tolerance in the roots. This reduc‑ tion of the chilling tolerance recovered with exogenously applied ethanol. Ethanol also induced 21‑ and 33‑kD protein synthesis in the roots and these proteins may contribute the improvement of the tolerance. The present research suggests that LT‑PT mayincrease chilling tolerance in rice roots owing to ethanol produc‑ tion, and ethanol may trigger a signal transduction cascade, which might lead to a decrease in membrane damage and injury. Alcohol dehydrogenase (ADH; EC.1.1.1.1) gene and protein were induced by low temperature in Arabidopsis, maize and rice seedlings.1,2,3 ADH is an enzyme involved in ethanolic fermentation and essential for plants tosurvive under anaerobic conditions.4,5 However, it is unlikely that the induction of ADH by low temperture is due to a switch from aerobic respiration to anaerobic respiration as reported with anaerobic conditions.2,6 Therefore, it is not clear that biological meanings of the induction of ADH in low temperature conditions. Rice seedlings (Oryza sativa L. cv. Nipponbare) were subjected to lowtemperature pretreatment (LT-PT; 10˚C) for various length of
Correspondence to: Hisashi Kato‑Noguchi; Department of Applied Biological Science; Faculty of Agriculture; Kagawa University, Miki, Kagawa 761‑0795 Japan; Fax.: +81.87.891.3086; Email: hisashi@ag.kagawa‑u.ac.jp Submitted: 02/27/08; Accepted: 01/08/08 Previously published online as a Plant Signaling & Behavior E‑publication:www.landesbioscience.com/journals/psb/article/5542 Addendum to: Kato‑Noguchi H. Low temperature acclimation to chilling tolerance in rice roots. Plant Growth Regul 2007; 51:171–5. 202

time (1, 2, 4, 6, 12, 18, 24 h) followed by a 48-h chilling temperature stress (2˚C). Chilling tolerance of rice roots was improved with increasing duration of LT-PT, but HT-PT longer than 12 h gave no additional improvement.LT-PT did not change in any fatty acid compositions in rice roots under the present experimental condition. Several plant species, such as oat, rye and spinach increased freezing tolerance due to the increasing unsaturation of fatty acids in plasma membranes, but this cold acclimation process required exposure of these plants to subzero temperature for 2–3 weeks.7,8 LT-PT increased ADH activity andethanol concentration in rice roots, and the activity and the concentration were increased with increasing duration of LT-PT up to 12 h. Thus, LT-PT induced ethanolic fermentation system and stimulated ethanol production in the roots. 4-Methylpyrazole, which is a potent inhibitor of ADH and prevents ethanol production,9 reduced rice root growth to 40% of LP-PT root growth (Fig. 1), and the...