Effects of gibberellic acid and environmental factors on cytosolic calcium in wheat aleurone cells

Abstract

Abstract. Gibberellins (GAs) control a wide range of physiological functions in plants from germination to flowering. The cellular mechanisms by which gibberellic acid (GA3) acts have been most extensively studied in the cereal aleurone. In this tissue, alterations in cellular calcium are known to be important for the primary response to GA, which is the production and secretion of hydrolytic enzymes. The extent to which cytosolic Ca 2 + mediates the early events in GA action, however, is not known. In order to address this question, changes in cytosolic Ca 2+ in wheat (Triticum aestivum L. cv. Inia) aleurone cells that occur rapidly after treatment with GA were characterized. In addition, GA-induced changes were compared with changes induced by three environmental stimuli that are known to modify the GA response: osmotic stress, salt (NaC1), and hypoxia. The Ca 2 +-sensitive dye fluo-3 was used to photometrically measure cytosolic Ca z+. It was found that GA3 induced a steady-state increase in cytosolic Ca 2 § of 100-500 nM. This increase was initiated within a few minutes of treatment with GA and was fully developed after 30-90 min. The changes in cytosolic Ca 2 + that were induced by GA were distinct from those induced by mannitol, NaC1, or hypoxia. Mannitol caused a steady-state decrease whereas NaC1 and hypoxia both increased cytosolic Ca 2 +. In the case of NaC1 this increase was transient but for hypoxia the increase was prolonged as long as hypoxic conditions were maintained. Gibberellin-induced changes in cytosolic Ca 2 § were not induced by the inactive GA, GAs, nor did the GA-insensitive wheat mutant, D6899, respond to active GA 3 with altered cytosolic Ca 2 § It is concluded that changes in cytosolic Ca 2 + are an early and integral part of the GA response in aleurone cells. The data also indicate, however, that changes in Ca 2 § are not sufficient, by themselves, to induce the GA response of aleurone cells.Abbreviations: AM = acetoxymethyl ester; GA = gibberellin; GA 3 = gibberellic acid; Mes = 2-[N-morpholino]ethanesulfonic acid; PM = plasma membrane

Signal Transduction in Barley Aleurone Protoplasts Is Calcium Dependent and Independent.

“…These results showing changes in cytoplasmic [Ca2+] in aleurone cells in response to GA and ABA, in conjunction with similar data from Jones (1987,1988), Gilroy and Jones (1992), and Bush (1996), present strong circumstantial evidence for changes in cytoplasmic Ca2+ being involved in some of the signal transduction andlor coordination of the aleurone cell response to GA and ABA. liowever, to test directly the role of cytosolic Ca2+ in regulating aleurone function, we microinjected protoplasts with Ca2+ and Ca2+ chelators to attempt to mimic or block the GA-and ABA-induced changes in cytoplasmic [Ca2+] noted above.…”

“…To assess the role of Ca2+ in the hormonal response of the aleurone cells, we first extended previous observations indicating that there is a steady state increase in Ca2+ in these cells in response to GA Jones, 1987, 1988;Gilroy and Jones, 1992;Bush, 1996). Ratio imaging of Ca2+ levels revealed a sustained increase in cytosolic Ca2+ from 100 to >600 nM in the peripheral cytoplasm when treated with GA ( Figure 2A).…”

“…Figure 2J shows the responses of three individual protoplasts that are representative of the range of responses (fastest to slowest, n = 28) seen. Heterogeneity of the Ca2+ response to GA has also been noted in wheat aleurone cells (Bush, 1996).…”

Gibberellins: regulating genes and germination

“…The cytoplasmic Ca# + concentration ([Ca# + ]) of barley and wheat aleurone cells is elevated from 100 n to around 500 n by GA, whereas ABA reduces Ca# + concentrations ( Fig. 3 a-c ; Bush & Jones, 1987, 1988Wang, Van-Duijn & Schram, 1991 ;Gilroy & Jones, 1992 ;van der Meulen, Visser & Wang, 1996 ;Bush, 1996 ;Gilroy, 1996). Calmodulin expression is also increased in response to GA (Fig.…”

The Effects of Calcium Nutrition on the Activities of Lactate Dehydrogenase, Alcohol Dehydrogenase and Other Enzymes in Melon (Cucumis melo L.) Seedlings Subjected to Flooding

“…알코올 가수분해효소 활성도 변화는 토마토 (Genez et al, 1993), 아라비돕시스 (Chung and Ferl, 1999), 귀리 (Biemelt et al, 1998), 보리 (Mayne and Lea, 1984), 옥수수 (Andrew et al, 1994), 벼 (Ismail et al, 2009), 두과작물 (Fukuda et al, 2005), 감자 (Matton et al, 1990) (Sedbrook et al, 1996;Chung and Ferl, 1999;Peng et al, 2001). 식 물체가 생육하고 있는 상태에서 산소가 부족해지면 세포질 내 칼슘의 농도가 빠르게 증가하는 경향이 있으며 이러한 조건에서는 액포 등에 저장된 칼슘이 세포질로 유리되는 것 으로 추정하고 있다 (Subbaiah et al, 1998 (Subbaiah et al, 1994;Bush, 1996;Sedbrook et al, 1996). 따라서 참외 유 …”