LOW-THRESHOLD LEVELS OF ULTRAVIOLET-B IN A BACKGROUND OF PHOTOSYNTHETICALLY ACTIVE RADIATION TRIGGER RAPID DEGRADATION OF THE D2 PROTEIN OFPHOTOSYSTEM-II
Mak. Jansen et al., LOW-THRESHOLD LEVELS OF ULTRAVIOLET-B IN A BACKGROUND OF PHOTOSYNTHETICALLY ACTIVE RADIATION TRIGGER RAPID DEGRADATION OF THE D2 PROTEIN OFPHOTOSYSTEM-II, Plant journal, 9(5), 1996, pp. 693-699
The photosystem II reaction centre has at its core a heterodimer made
up of two proteins, D1 and D2. The D1 protein is known to be rapidly d
egraded by photosynthetically active radiation while the D2 protein is
relatively stable. This paper reports that when the aquatic higher pl
ant, Spirodela was exposed to ultraviolet B radiation, D2 degradation
accelerated markedly and half life times approached those of the D1 pr
otein. Moreover, in the presence of an environmentally relevant backgr
ound of photosynthetically active radiation, low fluxes of ultraviolet
-B (but not ultraviolet-A) radiation synergistically stimulated degrad
ation of the D2 protein within functional reaction centres. Thus, abov
e a critical threshold, ultraviolet-B specifically targets the D1-D2 h
eterodimer for accelerated degradation.