High-Light Induced Proteins HL#2 of Barley are Exported to the Apoplast

Abstract

Light, when supplied in excess over the capacity of the electron transport chain, will be harmful to plants. This situation is tried to be prevented by the plants using different strategies. The first is to use uncoupling of the light harvesting antennae from the reaction centre on the short range and destruction of the light harvesting antennae during long-term adaptation to high light. During the process of adaptation also the composition in the Xanthophylls is changed by increasing the stationary concentrations of antheraxanthin (A), zeaxanthin (Z) and violaxanthin (V) as well as by simultaneously increasing the ratio of A+Z/V [6 and references therein]. But besides the mentioned and presumably some other short term regulations, long term changes in gene expression can be visualized which will include a great number of proteins. To these proteins belong obviously the ELIPs [1]. Starting from the assumption that these ELIPs would not be the only genes regulated by high light we used a differential cloning strategy by enriching for transcripts which are up-regulated by high light fluxes. Using this method clones were isolated which we termed “HL” for high light induced. Out of these, HL#2 represents a gene whose mRNA is up-regulated by high light fluxes. As described [8], sequence comparison showed similarity to proteins of rice. In the meantime cloning has considerably increased the number of related genes in the databank We find lectins and jasmonate-induced proteins among the related proteins some of which are also known to be regulated by light.