ИСТИНА

Phytochrome A (phyA) in the albina barley mutant (BGS 112, locus abo9) was characterized with the use of low-temperature (T=85K) fluorescence spectroscopy and photochemistry in coleoptiles of etiolated seedlings and after their light treatment, and also in dark-grown leaves. The following parameters of the pigment were evaluated: position (λmax) and half-band width (Δλ) of the emission spectrum, its content [Ptot], extent of the Pr→lumi-R conversion at 85 K (γ1) and, from this parameter, proportion of the two phyA native pools – photochemically active and inactive at low T – phyA' and phyA'', respectively (Sineshchekov, 2010). In etiolated coleoptiles of strip and mutant plants, spectroscopic properties of phyA were the same with λmax =683 nm and Δλ=27 nm, and [Ptot], γ1 and proportion of the two phyA pools (phyA'/phyA'', %) did not vary considerably between the strip and the mutant (3.29±0.18 rel. units, 0.45±0.02 and 90/10% vs. 4.25±0.36 rel. units, 0.48±0.02 and 96/4%, respectively). phyA also revealed similar light-lability: illumination brought about [Ptot] decline by approx. 3-fold in mutant and strip coleoptiles and preferential reduction of phyA’ shifting the equilibrium towards phyA'' (to 14/86% in albina vs. 30/70% in strip). However, there was a considerable difference between these two lines in the state of phyA in etiolated leaves: the pigment in the mutant leaves, which was spectroscopically and photochemically similar to that in the coleoptiles with the same phyA'/phyA'' ratio of 90/10%, had substantially higher [Ptot] than that in the strip leaves (≥10-fold). Thus, we may conclude that the albina abo9 mutation in barley modifies phyA biosynthesis and/or destruction increasing its content, and this effect reveals tissue/organ dependency affecting phyA state primarily in etiolated leaves.