Genome-wide Characterization of LBD Transcription Factors in Switchgrass (Panicum Virgatum L.) and the Involvement of PvLBD12 in Salt Tolerance

PvLBD12 enhanced the salt tolerance by increasing proline accumulation, improving K accumulation, and decreasing reactive oxygen species level in switchgrass. Abiotic stresses are the serious factors which limit plant development and productivity and restrict the agricultural economy. It is important, therefore, to understand the mechanism of abiotic tolerance in plants. Lateral organ boundaries domain (LBD) proteins as plant-specific transcription factors play important function in plant lateral organ development, plant regeneration, and abiotic stress. In our study, we identify 69 LBD members from switchgrass genome-wide sequences and classify them based on their homology with LBD proteins in Arabidopsis. RT-qPCR showed that PvLBD genes had different expression patterns under abiotic stress conditions, indicating that they play important roles in various stress. PvLBD12 was selected as a candidate gene for further functional analysis because it had the highest expression level under salt stress. Overexpression of PvLBD12 enhanced salt tolerance by altering a wide range of physiological responses (like increased proline accumulation, reduced malondialdehyde production, improved K accumulation, and reduced Na absorption) in switchgrass. Some stress response genes such as proline biosynthesis gene PvP5CS1, vacuolar Na(K)/H antiporter gene PvNHX1, two key ROS-scavenging enzyme genes PvCAT and PvSOD were all upregulated in PvLBD12 overexpression lines. Taken together, PvLBD12 plays a pivotal role in response to salt stress by increasing proline accumulation, improving K accumulation, reducing Na absorption, and decreasing reactive oxygen species level. It will be better to understand the potential biological functions of LBD genes in other plants.