A. Gali et al., THE EFFECT OF LIGHT INTENSITIES ON THE TRANSCRIPT LEVEL OF PROTEINS INVOLVED IN PHOTOSYNTHESIS IN MUSTARD PLANTS, Journal of plant physiology, 149(1-2), 1996, pp. 79-85
The influence of light quantity on the steady-state levels of plastid
encoded transcripts was examined during the development of primary lea
ves from mustard (Sinapis alba) plants. RbcL mRNA, petA mRNA, and psbA
mRNA, which encode the large subunit (LSU) of Rubisco, Cyt f of the C
yt b(6)/f complex, and D 1 protein of PSII were investigated in leaves
grown under high-light (HL) or low-light (LL) conditions. Additionall
y, the nuclear encoded 25 S rRNA was quantified. As a proportion of to
tal RNA, the levels of 25 S rRNA, rbcL mRNA, petA mRNA, and psbA mRNA
did not differ substantially in the HL versus LL plants. During leaf o
ntogenesis, though, the proportion of psbA mRNA in total RNA increased
drastically, in contrast to the other transcripts. The results calcul
ated per unit fresh weight, dry weight, leaf area, and chlorophyll clo
sely resembled each other and gave an idea of the absolute prevalence
of the transcripts in the cell. The light regime had a remarkable infl
uence on the absolute levels of 25 S rRNA, rbcL mRNA, and petA. mRNA:
Paralleling total RNA content, the amounts of the three transcripts pe
r unit fresh weight at the beginning of leaf development were, in HL p
lants, more than twice the amounts found in LL plants. Furthermore, du
ring leaf ontogenesis the decrease in total RNA, 25 S rRNA, rbcL mRNA,
and petA mRNA was more pronounced in HL than in LL, while the psbA mR
NA content per unit fresh weight was only slightly higher in HL than i
n LL leaves and did not decline significantly during HL and LL leaf on
togenesis. Comparison of the absolute levels of rbcL mRNA, petA mRNA,
and psbA mRNA with the amounts of the corresponding proteins revealed
that the prevalence of the transcripts contributes principally to the
differences in the protein content in HL and LL leaves.