Regulation of long noncoding RNA(LNCRNA) in response to spike disease in santalum album Linn.

Abstract

Sandalwood (Santalum album Linn.), is listed as vulnerable on the IUCN Red List. The tree is highly priced for its aromatic heartwood and essential oil which is used for many medicinal purposes and perfumery. One of the major reason for decline in population is the Sandal Spike Disease (SSD) caused by a phytoplasma which often lead to the death of the plants. No effective measures for recovering diseased plants from the spike disease have been identified and removal of diseased trees from the field is considered as the usual method for controlling the spread of the disease. Many studies were carried out in agricultural crops and tree to elucidate the role of the lncRNA both in biotic and abiotic stress response. Identifying the spike responsive lncRNA and analysing the expression level of these lncRNA will help in developing management strategies for sandal spike disease. Reserve No. 52 of Marayoor sandal division is mostly infected with spike disease and is selected as the study location. Based on morphological characters observed in the field, 15 trees were marked as spike infected and 15 trees as non infected. Molecular level disease confirmation was carried out in these 30 selected samples using reported SSD I primer pair for 16sRNA for sandal spike phytoplasma. It was found that among designated 15 non infected trees, two were infected. Bimonthly observations on leaf area (cm2), leaf thickness (mm) and total chlorophyll (mg g-1) content were made. These morphological parameters were significantally varied between spike infected and non-infected trees. Earlier reported six phytoplasma responsive lncRNAs were amplified in the genomic DNA of sandalwood. Differential expression of these six lncRNAs were analyzed by Q RT PCR method and 2–∆∆Ct method. Among the lncRNAs analysed, TCONS_00021785, TCONS_00019890, TCONS_00004908 were down regulated and TCONS_00012735, TCONS_00033648, TCONS_00034613 were upregulated in the spike infected samples. In earlier studies, these phytoplasma responsive lncRNAs were reported 90 to play a key role in defense mechanism, photosynthesis, metabolism, stress resistance and cell signal transduction. Analysing the expression profile of spike responsive lncRNAs at regular interval in more number of trees will throw light on how the lncRNA is regulated on the progression of the sandal spike disease compared to non infected plants. Identification of more number of spike responsive lncRNA will be helpful in using as a biomarker for the early detection of spike disease, even if the symptom is not present in the plant. Understanding the role of these lncRNAs in defensive signaling pathway will help to regulate the pathway in desirable manner.