DhEFL2, 3 and 4, the three EARLY FLOWERING4-like genes in a Doritaenopsis hybrid regulate floral transition

Abstract

DhEFL2, 3 and 4 regulate the flowering of Doritaenopsis . These genes could rescue elf4-1 phenotype in Arabidopsis while its overexpression delayed flowering. Phalaenopsis are popular floral plants, and studies on orchid flowering genes could help develop off-season cultivars. Early flowering 4 (ELF4) of A. thaliana has been shown to be involved in photoperiod perception and circadian regulation. We isolated two members of the ELF4 family from Doritaenopsis hybrid (Doritaenopsis 'Tinny Tender' (Doritaenopsis Happy Smile × Happy Valentine)), namely, DhEFL2 and DhEFL3 (DhEFL4 has been previously cloned). Multiple alignment analysis of the deduced amino acid sequences of the three DhEFL homologs showed that DhEFL4 and DhEFL2 are similar with 72% identical amino acids, whereas DhEFL3 is divergent with 72% similarity with DhEFL2 and 68% similarity with DhEFL4. DhEFL3 forms a separate phylogenetic subgroup and is far away from DhEFL2 and DhEFL4. The diurnal expression patterns of DhEFL2, 3, and 4 are similar in the long-day photoperiod conditions; however, in the short-day conditions, DhEFL3 is different from DhEFL2 and 4. For the DhEFL2, 3, and 4 genes, the strongest audience expression organs are the stem, petal and bud, respectively. The ectopic expression of DhEFL2, 3, or 4 in transgenic A. thaliana plants (Ws-2 ecotype) showed novel phenotypes by late flowering and more rosette leaves. The ectopic expression of DhEFL2, 3, or 4 could complement the elf4-1 flowering time and hypocotyl length defects in transgenic A. thaliana elf4-1 mutant plants. These results strongly suggest that DhEFL2, 3, and 4 may be involved in regulation of flower formation and floral induction in Doritaenopsis.

Floral Induction and Flower Development of Orchids

“…Flowering of Dortiaenopsis (now Phalaenopsis ) is promoted by low ambient temperature (22 °C/18 °C, day/night) (Luo et al, 2011) and the expression of DhFVE is increased in the stem during floral transition. In addition, EARLY FLOWERING 4 ( EFL4 ) family genes, DhEFL2 , DhEFL3 and DhEFL4 have been identified in Dortiaenopsis (Chen et al, 2015). Arabidopsis EFL4 is known to affect flowering through photoperiod perception and circadian regulation (Doyle et al, 2002).…”

“…The CO in Phalaenopsis may also activate FT irrespective of photoperiod (Zhang et al, 2011; Kaewphalug et al, 2017). In addition, ELF genes in Phalaenopsis may repress the CO activity (Doyle et al, 2002; Chen et al, 2015). Moreover, the GI-FLAVIN-BINDING, KELCH REPEAT, F BOX 1 (FKF1) and CYCLING DOF FACTOR (CDF) may also regulate the CO activity in Phalaenopsis as is also the case in Arabidopsis (Song, 2016).…”

Genome-Wide Identification of the Early Flowering 4 (ELF4) Gene Family in Cotton and Silent GhELF4-1 and GhEFL3-6 Decreased Cotton Stress Resistance

“…EC can inhibit the expression of phytochrome interacting factor 4 ( PIF4 ) and PIF5 expression in the evening, leading to hypocotyl elongation ( Nusinow et al, 2011 ). Furthermore, it was found that the hypocotyl of elf4-1 mutant is longer than the wild type in Arabidopsis ( Chen et al, 2015a ). DhEFL2 , 3 , and 4 of Doritaenopsis hybrid ELF4 family gene can rescue elf4 mutant growth phenotype ( Chen et al, 2015a ).…”

“…Furthermore, it was found that the hypocotyl of elf4-1 mutant is longer than the wild type in Arabidopsis ( Chen et al, 2015a ). DhEFL2 , 3 , and 4 of Doritaenopsis hybrid ELF4 family gene can rescue elf4 mutant growth phenotype ( Chen et al, 2015a ).…”

“…In the flowering study, the expression of AtCO and AtFT decreased after GmELF4 gene of soybeans overexpression resulted in delayed flowering ( Juliana et al, 2017 ). Doritaenopsis hybrid genes DhEFL2 , 3 , and 4 are also related to flowering regulation ( Chen et al, 2015a ). And studies have found that ELF4 inhibits the expression of CO , causing the elf4-1 mutant to show early flowering ( Doyle et al, 2002 ).…”