Abstract
Because of the long and unpredictable flowering period in bamboo, the molecular mechanism of bamboo flowering is unclear. Recent study showed that Arabidopsis PIN1-type parvulin 1 (Pin1At) is an important floral activator and regulates floral transition by facilitating the cis/trans isomerization of the phosphorylated Ser/Thr residues preceding proline motifs in suppressor of overexpression of CO 1 (SOC1) and agamous-like 24 (AGL24). Whether bamboo has a Pin1 homolog and whether it works in bamboo flowering are still unknown. In this study, we cloned PvPin1, a homolog of Pin1At, from Phyllostachys violascens (Bambusoideae). Bioinformatics analysis showed that PvPin1 is closely related to Pin1-like proteins in monocots. PvPin1 was widely expressed in all tested bamboo tissues, with the highest expression in young leaf and lowest in floral bud. Moreover, PvPin1 expression was high in leaves before bamboo flowering then declined during flower development. Overexpression of PvPin1 significantly delayed flowering time by downregulating SOC1 and AGL24 expression in Arabidopsis under greenhouse conditions and conferred a significantly late flowering phenotype by upregulating OsMADS56 in rice under field conditions. PvPin1 showed subcellular localization in both the nucleus and cytolemma. The 1500-bp sequence of the PvPin1 promoter was cloned, and cis-acting element prediction showed that ABRE and TGACG-motif elements, which responded to abscisic acid (ABA) and methyl jasmonate (MeJA), respectively, were characteristic of P. violascens in comparison with Arabidopsis. On promoter activity analysis, exogenous ABA and MeJA could significantly inhibit PvPin1 expression. These findings suggested that PvPin1 may be a repressor in flowering, and its delay of flowering time could be regulated by ABA and MeJA in bamboo.
Highlights
The transition from vegetative to reproductive growth must start at an appropriate time in flowering plants for producing progeny and perpetuating the species
Using gene-specific primers, a 744-bp cDNA sequence of Pin1-like was isolated from P. violascens by using 3 and 5 rapid amplification of cDNA ends (RACE) and designated as PvPin1
Comparison of the genomic DNA sequence and open reading frame (ORF) sequences showed that PvPin1 had two exons (248 and 121 bp) and one intron (2709 bp) (Figure 1A), which was same as Pin1At (Landrieu et al, 2000) and Pin1-like in rice (NCBI Oryza sativa Japonica Group Annotation Release 101)
Summary
The transition from vegetative to reproductive growth must start at an appropriate time in flowering plants for producing progeny and perpetuating the species. Bamboo is a kind of widespread, fast-growing, renewable, and environmental-enhancing resource, whose industry contributes to providing food, building materials, and increasing the income for 2.2 billion people in the world (Chen, 2003). Bamboo products such as bamboo shoots, furniture, flooring, charcoal, beverages, and cosmetic are being used and traded by half of the world’s population (Chen, 2003). Louis et al (2015) used proteomics to find that elements of stress, mobile genetics, and signal transduction cross-talk were associated with sporadic flowering of bamboo These results provide the basis for understanding the roles of genes involved in bamboo flowering but need further experimental evidence
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