Induction ofent-kaurene biosynthesis by low temperature in dwarf peas

Abstract

Abstract. Germinating pea (Pisum sativum L.) seeds of two dwarf cultivars, "Progress No. 9" and "Green Arrow," and two tall cultivars, "Alaska" and "Alderman," were treated with low temperature (3-5~ for 14 days and then transferred to normal growing conditions (19-21~ for 16 h/14.5-16.5~ for 8 h) for an additional 10 days. Biosynthesis of [14C]ent-kaurene from [14C]2-mevalonic acid (2-MVA) was assayed in cell-free enzyme extracts prepared from shoot tips 10 days after cold treatment and was compared with activity in enzyme extracts prepared from noncold-treated, 10-day-old control plants. Shoot lengths of coldtreated plants were measured throughout a 35-day period and compared with shoot lengths of plants grown without cold treatment for 25-35 days. Low temperature induced a five-to 10-fold enhancement of ent-kaurene, hence potentially gibberellin (GA), biosynthesis in seedlings of the two dwarf cultivars but not in the tall cultivars. However, the lack of an increase in growth rate in the cold-treated dwarfs indicated that endogenous GA biosynthesis remained blocked at some point beyond ent-kaurene in the biosynthetic pathway. Since the lateflowering "Alderman" cultivar did not exhibit enhanced biosynthesis of ent-kaurene, it appears that if vernalization in late-flowering cultivars of peas is correlated with enhanced GA biosynthesis, it is not the early part of the biosynthetic pathway which is affected.The many commercial cultivars of pea (Pisum sativum L.) are categorized as dwarf and tall and as early-flowering and late-flowering. Dwarf cultivars generally mature at shoot heights of approximately 30 cm or less, whereas tall cultivars may exceed 1 m. Late-flowering cultivars typically flower above the 15th node, respond to photoperiod as quantitative long-day plants, and are vernalizable. In contrast, early-flowering cultivars flower at the 9th or 10th node above the cotyledons, behave as dayneutral plants, and are not vernalizable (Barber 1959, Marx 1977, Moore 1964, Moore and Bonde 1962, Muffet 1977, Reid 1988, Reid and Muffet 1975.Vernalization of late-flowering cultivars of pea, that is, treatment of germinating seeds with low temperature for one to several weeks to induce early flowering, has been investigated extensively (Barber 1959, Highkin 1956, Moore and Bonde 1958, 1962, Reid and Muffet 1975. Highkin (1956) first reported that late-flowering cultivars are vernalizable with respect to both flower formation and vegetative development. The inductive effect of cold treatment on flowering is manifested as a reduction in the number of nodes to flower and the number of days to anthesis. The inductive effect of low temperature on vegetative development is a reduction in the amount of vegetative growth accompanying flowering (i.e., height to the first flowering node). Highkin termed the latter effect "vegetative vernalization" (Highkin 1956).The purpose of the present investigations was to test the hypothesis that vernalization of lateflowering cultivars of peas is correlated with enhanced biosynthesis of...

Yield Pattern of Sugar Peas Cultivars as Influenced By Planting Dates to Meet The Export Requirements

“…These agree with Moore and Moore (1991). They found that peas plants grown underlow temperature helped gibberellin biosynthesis for enhancing plant growth, when transferred to normal growing conditions.…”

The Arabidopsis GA1 locus encodes the cyclase ent-kaurene synthetase A of gibberellin biosynthesis.

“…Because entkaurene is a key intermediate in the GA pathway, its synthesis is likely to be a regulatory point for GA biosynthesis. Indeed, ent-kaurene production has been shown to be altered by changes in photoperiod, temperature, and growth potential of tissues in certain species (Chung and Coolbaugh, 1986;Moore and Moore, 1991;Zeevaart and Gage, 1993).…”

The GA2 Locus of Arabidopsis thalianaEncodes ent-Kaurene Synthase of Gibberellin Biosynthesis

“…Biochemical studies suggested that CPS and KS may interact with each other (Duncan and West, 1981) and that these enzymes are localized in plastids (Railton et al, 1984;Sun and Kamiya, 1994; Aach et al, 1995). There is some evidence that ent-kaurene biosynthesis is controlled by environmental conditions such as photoperiod (Zeevaart and Gage, 1993) and temperature (Moore and Moore, 1991), as well as during plant development (Chung and Coolbaugh, 1986;Silverstone et al, 1997).From Arabidopsis thaliana six GA-responsive dwarf mutants (ga1 through ga6) have been isolated and characterized (Koornneef and van der Veen, 1980;Sponsel et al, 1997). Each mutant is blocked in a specific step in GA biosynthesis.…”