Genome-Wide Identification and Expression Analyses of the Fibrillin Family Genes Suggest Their Involvement in Photoprotection in Cucumber

Abstract

Fibrillin (FBN) is a plastid lipid-associated protein found in photosynthetic organisms from cyanobacteria to plants. In this study, 10 <i>CsaFBN</i> genes were identified in genomic DNA sequences of cucumber (Chinese long and Gy14) through database searches using the conserved domain of FBN and the 14 <i>FBN</i> genes of Arabidopsis. Phylogenetic analysis of CsaFBN protein sequences showed that there was no counterpart of Arabidopsis and rice FBN5 in the cucumber genome. FBN5 is essential for growth in Arabidopsis and rice; its absence in cucumber may be because of incomplete genome sequences or that another FBN carries out its functions. Among the 10 <i>CsaFBN</i> genes, <i>CsaFBN1</i> and <i>CsaFBN9</i> were the most divergent in terms of nucleotide sequences. Most of the <i>CsaFBN</i> genes were expressed in the leaf, stem and fruit. <i>CsaFBN4</i> showed the highest mRNA expression levels in various tissues, followed by <i>CsaFBN6</i>, <i>CsaFBN1</i> and <i>CsaFBN9</i>. High-light stress combined with low temperature decreased photosynthetic efficiency and highly induced transcript levels of <i>CsaFBN1</i>, <i>CsaFBN6</i> and <i>CsaFBN11</i>, which decreased after 24 h treatment. Transcript levels of the other seven genes were changed only slightly. This result suggests that CsaFBN1, CsaFBN6 and CsaFBN11 may be involved in photoprotection under high-light conditions at low temperature.