Influence of EARLI1‐like Genes on Flowering Time and Lignin Synthesis of Arabidopsis thaliana
EARLI1 encodes a 14.7 kDa protein in the cell wall, is a member of the PRP (proline‐rich protein) family and has multiple functions, including resistance to low temperature and fungal infection. RNA gel blot analyses in the present work indicated that expression of EARLI1‐like genes, EARLI1, At4G12470 and At4G12490, was down‐regulated in Col‐FRI‐Sf2 RNAi plants derived from transformation with Agrobacteriumstrain ABI, which contains a construct encoding a double‐strand RNA targeting 8CM of EARLI1. Phenotype analyses revealed that Col‐FRI‐Sf2 RNAi plants of EARLI1 flowered earlier than Col‐FRI‐Sf2 wild‐type plants. The average bolting time of Col‐FRI‐Sf2 and Col‐FRI‐Sf2 RNAi plants was 39.7 and 19.4 days, respectively, under a long‐day photoperiod. In addition, there were significant differences in main stem length, internode number and rosette leaf number between Col‐FRI‐Sf2 and Col‐FRI‐Sf2 RNAi plants. RT‐PCR showed that EARLI1‐like genes might delay flowering time through the autonomous and long‐day photoperiod pathways by maintaining the abundance of FLC transcripts. In Col‐FRI‐Sf2 RNAi plants, transcription of FLC was repressed, while expression of SOC1 and FT was activated. Microscopy observations showed that EARLI1‐like genes were also associated with morphogenesis of leaf cells in Arabidopsis. Using histochemical staining, EARLI1‐like genes were found to be involved in regulation of lignin synthesis in inflorescence stems, and Col‐FRI‐Sf2 and Col‐FRI‐Sf2 RNAi plants had 9.67% and 8.76% dry weight lignin, respectively. Expression analysis revealed that cinnamoyl‐CoA reductase, a key enzyme in lignin synthesis, was influenced by EARLI1‐like genes. These data all suggest that EARLI1‐like genes could control the flowering process and lignin synthesis in Arabidopsis.