Isolation and characterization of proline/betaine transporter gene from oil palm

Genome-Wide Identification of Proline Transporter Gene Family in Non-Heading Chinese Cabbage and Functional Analysis of BchProT1 under Heat Stress

Non-heading Chinese cabbage prefers cool temperatures, and heat stress has become a major factor for reduced yield. The proline transporter protein (ProT) is highly selective for proline transport, contributing to the heat tolerance of non-heading Chinese cabbage. However, there has been no systematic study on the identification and potential functions of the ProT gene family in response to heat stress in non-heading Chinese cabbage. We identified six BchProT genes containing 11-12 transmembrane helices characteristic of membrane proteins through whole-genome sequencing. These genes diverged into three evolutionary branches and exhibited similarity in motifs and intron/exon numbers. Segmental duplication is the primary driving force for the amplification of BchProT. Notably, many stress-related elements have been identified in the promoters of BchProT using cis-acting element analysis. The expression level of BchProT6 was the highest in petioles, and the expression level of BchProT1 was the highest under high-temperature stress. Subcellular localization indicated their function at cell membranes. Heterologous expression of BchProT1 in Arabidopsis plants increased proline transport synthesis under heat-stress conditions. This study provides valuable information for exploring the molecular mechanisms underlying heat tolerance mediated by members of the BchProT family.

Exogenous proline has favorable effects on growth and browning suppression in rice but not in tobacco

Proline is one of the amino acids that compose proteins and has various roles under non-stress and stress conditions. In this study, we investigated the effect of proline on the growth and browning of two plants, tobacco and rice, by exogenous application and endogenous increase of proline. Exogenous proline had a different effect on the growth and browning between tobacco and rice: proline affected negatively the growth of tobacco seedlings and favorably that of rice seedlings. In addition, proline prevented browning only in rice cultured cells, consistent with the increase of proline contents, but not in tobacco BY-2 cells. These results might be due to the difference of exogenous proline uptake activity in these cells. From the Lineweaver-Burk plots, proline inhibited polyphenol oxidase activity in vitro, which is a major factor of enzymatic browning in plants, by affecting the enzyme-substrate complex. Proline could suppress the browning of the plant callus by inhibition of PPO activity.