Karpinski S, Karpinska B, Wingsle G, Hallgren JE
Molecular Responses to Photooxidative Stress in Pinus-Sylvestris .1. Differential Expression of Nuclear and Plastid Genes in Relation to Recovery from Winter Stress
Physiologia Plantarum: 1994 90:358-366
Inhibition of photosynthesis plays an important role during winter-spring stress in evergreen plants such as Scots pine (Pinus sylvestris L.). In this experiment, naturally established three-year-old Scots pine seedlings were studied during recovery from winter stress, under natural conditions from May to the beginning of June. A comparison was made between top shoot needles exposed to sun and, prior to winter stress recovery snow-covered, and thus more shaded side shoot needles. Chlorophyll fluorescence, photochemical and non-photochemical quenching, pigment composition together with the Lhca2*1, Lhcbl*2, RbcS, rbcL, psbA, nad3 and cox2 gene expression were analysed. During the recovery, a general increase in the F(v)/F(m) ratio of chlorophyll fluorescence and in pigments was observed for both types of shoots. At the beginning of May, the F(v)/F(m) ratio of chlorophyll fluorescence showed that exposed top shoot needles were more photoinhibited than the snow-covered side shoot needles. The levels of chlorophyll a and b, neoxanthin, alpha- and beta-carotene were lower, while the level of zeaxanthin was higher in top shoot needles than in side shoot needles during the whole period. On May 6, significantly higher (two-fold) mRNA levels for Lhca2*1 and Lhcb1*2 genes were detected in top shoot needles than in side shoot needles. The reverse situation for these genes was observed on May 19 with a two-fold higher level of mRNA in side shoot needles. The transcript level was significantly higher for the Lhcb1*2 gene than for the Lhca2*1 gene in both types of shoots only at the beginning of May. The mRNA level for the RbcS gene on May 4 and 6 was two- and four-fold higher, respectively, in top than in side shoot needles. The transcript levels for the plastid-encoded rbcL and psbA and for the mitochondrion-encoded nad3 and cox2 genes were constant and similar in top and side shoot needles. The results are discussed in relation to recovery from winter-spring stress and observed differential expression of nuclear- and organellar-encoded genes.
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