Abstract
Lysine (Lys) is indispensable nutritionally, and its levels in plants are modulated by both transcriptional and post-transcriptional control during plant ontogeny. Animal glutamate receptor homologs have been detected in plants, which may participate in several plant processes through the Lys catabolic products. Interestingly, a connection between Lys and serotonin metabolism has been established recently in rice. 2-Aminoadipate, a catabolic product of Lys appears to play a critical role between serotonin accumulation and the color of rice endosperm/grain. It has also been shown that expression of some lysine-methylated proteins and genes encoding lysine-methyltransferases (KMTs) are regulated by cadmium even as it is known that Lys biosynthesis and its degradation are modulated by novel mechanisms. Three complex pathways co-exist in plants for serine (Ser) biosynthesis, and the relative preponderance of each pathway in relation to plant development or abiotic stress tolerance are being unfolded slowly. But the phosphorylated pathway of L-Ser biosynthesis (PPSB) appears to play critical roles and is essential in plant metabolism and development. Ser, which participates indirectly in purine and pyrimidine biosynthesis and plays a pivotal role in plant metabolism and signaling. Also, L-Ser has been implicated in plant responses to both biotic and abiotic stresses. A large body of information implicates Lys-rich and serine/arginine-rich (SR) proteins in a very wide array of abiotic stresses. Interestingly, a link exists between Lys-rich K-segment and stress tolerance levels. It is of interest to note that abiotic stresses largely influence the expression patterns of SR proteins and also the alternative splicing (AS) patterns. We have checked if any lncRNAs form a cohort of differentially expressed genes from the publicly available PPSB, sequence read archives of NCBI GenBank. Finally, we discuss the link between Lys and Ser synthesis, catabolism, Lys-proteins, and SR proteins during plant development and their myriad roles in response to abiotic stresses.
Highlights
Amino acids are organic compounds, which contain amine (-NH2) and carboxyl C(=O)OH) functional groups along with a side chain (R group)
This review focuses on the climacteric links that have been established in recent times about Lys and Ser biosynthesis and catabolism, their association with plant growth and development, abiotic stress tolerance, and Lys- and Ser-rich proteins, functional significance, and their remarkable ability to bestow stress tolerance in plants
Among the pathways that exist, the phosphorylated pathway of L-Ser biosynthesis (PPSB) appears to play a critical role during growth and development
Summary
Amino acids are organic compounds, which contain amine (-NH2) and carboxyl C(=O)OH) functional groups along with a side chain (R group). A large body of information suggests that the regulatory networks associated with Lys biosynthesis and catabolism are intertwined largely with plant tissues and organ specificity and interactions between diverse metabolic fluxes Another important amino acid in the body of plants is serine (Ser), which helps to form the phospholipids necessary for signal transduction. The enzyme L,L-diaminopimelate aminotransferase (LL-DAP-AT) is a novel variant that catalyzes tetrahydrodipicolinate to L,L-DAP and helps in the synthesis of Lys in lower plants (Physcomitrella patens) as well as higher plants like A. thaliana, soybean, and spinach (Hudson et al, 2006). This indicates that the enzyme is highly conserved among diverse plant species. Diaminopimelate epimerase is the last enzyme in the pathway, which converts m-DAP to Lys (Figure 1A)
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