AUTHOR=Zheng Zhigang , Yang Xiaoming , Fu Yaping , Zhu Longfei , Wei Hantian , Lin Xinchun 

TITLE=Overexpression of PvPin1, a Bamboo Homolog of PIN1-Type Parvulin 1, Delays Flowering Time in Transgenic Arabidopsis and Rice

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01526

DOI=10.3389/fpls.2017.01526

ISSN=1664-462X

ABSTRACT=<p>Because of the long and unpredictable flowering period in bamboo, the molecular mechanism of bamboo flowering is unclear. Recent study showed that <italic>Arabidopsis</italic> PIN1-type parvulin 1 (Pin1At) is an important floral activator and regulates floral transition by facilitating the <italic>cis/trans</italic> 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 <italic>Pin1</italic> homolog and whether it works in bamboo flowering are still unknown. In this study, we cloned <italic>PvPin1</italic>, a homolog of <italic>Pin1At</italic>, from <italic>Phyllostachys violascens</italic> (Bambusoideae). Bioinformatics analysis showed that PvPin1 is closely related to Pin1-like proteins in monocots. <italic>PvPin1</italic> was widely expressed in all tested bamboo tissues, with the highest expression in young leaf and lowest in floral bud. Moreover, <italic>PvPin1</italic> expression was high in leaves before bamboo flowering then declined during flower development. Overexpression of <italic>PvPin1</italic> significantly delayed flowering time by downregulating <italic>SOC1</italic> and <italic>AGL24</italic> expression in <italic>Arabidopsis</italic> under greenhouse conditions and conferred a significantly late flowering phenotype by upregulating <italic>OsMADS56</italic> in rice under field conditions. PvPin1 showed subcellular localization in both the nucleus and cytolemma. The 1500-bp sequence of the <italic>PvPin1</italic> promoter was cloned, and <italic>cis</italic>-acting element prediction showed that ABRE and TGACG-motif elements, which responded to abscisic acid (ABA) and methyl jasmonate (MeJA), respectively, were characteristic of <italic>P. violascens</italic> in comparison with <italic>Arabidopsis</italic>. On promoter activity analysis, exogenous ABA and MeJA could significantly inhibit <italic>PvPin1</italic> expression. These findings suggested that <italic>PvPin1</italic> may be a repressor in flowering, and its delay of flowering time could be regulated by ABA and MeJA in bamboo.</p>