PHYSIOLOGICAL RESPONSES TO PHOSPHORUS LIMITATION IN BATCH AND STEADY-STATE CULTURES OF <em>DUNALIELLA TERTIOLECTA</em> (CHLOROPHYTA): A UNIQUE STRESS PROTEIN AS AN INDICATOR OF PHOSPHATE DEFICIENCY.

Graziano, Lisa M.; Roche, Julie La; Geider, Richard J.

A protein unique to phosphorus stress observed in Dunaliella tertiolecta Butcher was studied in the context of phosphate-limited cell physiology and is a potential diagnostie indicator of phosphate deficiency in this alga. Cells were grown over a range of limited, steady-state growth rates and at maximum (replete) and zero (phosphate-starved) growth rates. The stress protein, absent in nutrient-replete cells, was produced under all steady-state phosphate-limited conditions and increased in abundance with increasing limitation (decreasing growth rate). Cellular carbon: phosphorus ratios and the maximum uptake rates of phosphate (V[subm]) increased with increasing limitation, whereas the ration of chlorophyll a: carbon decreased. Alkaline phosphatase activity did not respond to limitation but was measurable in starved, stationary-phase cells F[subv]/F[subm] a measure of photochemical efficiency, was a nonlinear, saturating function of μ, as commonly observed under N limitation. The maximum F[subv]/F[subm] of 0.64 was measured in nutrient-replete cells growing at μ[submax] and a value of zero was measured in stationary-phase starved cells. When physiological parameters were compared, the P-stress protein abundance and F[subv]/F[subm] were the most sensitive indicators of the level of deficiency. The stress protein was nor produced under N-or Fe-limited conditions. It is of high molecular weight (>200) and is associated with internal cell membranes. The stress protein has several characteristics that make it a potential diagnostic indicator: it is 1) unique to phosphorus limitation (i.e. absent under all other conditions), 2) present under limiting as well as starved condition, 3) sensitive to the level of limitation, and 4) observable without time-course incubation of live samples.

DUNALIELLA; GREEN algae; PHOSPHORUS; HEAT shock proteins; POLYBLEPHARIDACEAE; PHOSPHATES

Journal of Phycology, 1996, Vol 32, Issue 5, p825

0022-3646

Academic Journal

10.1111/j.0022-3646.1996.00825.x