Differential Expression of Phenylalanine Ammonia- Lyase in Different Tissues of Sugarcane (Saccharum officinarum L.) during Development

The phenylpropanoid pathway serves as a rich source of metabolites in plants. It is required for the biosynthesis of lignin and acts as a starting point for the production of many other important compounds involved in growth and development. Phenylalanine ammonia-lyase (PAL) catalyzes the first step of the phenylpropanoid pathway. PAL gene expression changes during the growth and development of plants as it regulates the synthesis of lignin and other phenylpropanoid compounds. The gene expression of sugarcane (Saccharum officinarum L.) PAL (SoPAL) was analyzed using quantitative real-time PCR (qPCR) and the comparative ΔΔCt method in different tissues during different developmental stages. The results showed that SoPAL was expressed in all tissues and developmental stages. SoPAL mRNA levels were increased from germination to tillering stages, except in the sheath, and from tillering to grand growth stages in the leaf and stem. PAL expression decreased from the grand growth to maturation stages in all tissues except the sheath. The highest expression of SoPAL occurred in the stem during the grand growth stage, while its lowest expression occurred in the leaf during germination (p<0.05). In conclusion, PAL, as a rate-limiting enzyme of the phenylpropanoid pathway, displays critical roles in the development of sugarcane, particularly in lignified tissues.