Mainaak Mukhopadhyay

Structural, physiological, and biochemical profiling of tea plantlets under zinc stress

Zinc is the most widespread deficient micronutrient in the tea growing soils of India which affects growth of the plants. In order to investigate the structural, physiological, and biochemical changes under Zn stress (i.e. both deficient and excess supply) of tea [Camellia sinensis (L.) O. Kuntze cv. T-78] plants, we treated young plants with ZnSO4 at 0 (deficiency), 0.3, 3 (optimum), and 30 μM (toxic) concentrations for 8 weeks. Zn deficiency and excess resulted in considerable decrease in shoot and root fresh and dry masses, and transmission electron microscopy (TEM) revealed disorganization of some cellular organelles. Further, Zn-stress decreased net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (gs), and content of chlorophylls a and b. On the other hand, content of superoxide anion, malondialdehyde, hydrogen peroxide, and phenols, and electrolyte leakage were elevated in stressed plants. The activities of ascorbate peroxidase, catalase, superoxide dismutase, and peroxidase as well as expression of respective genes were up-regulated under Zn-stress. Nevertheless, antioxidant system as a whole did not afford sufficient protection against oxidative damage.

Generation and characterization of expressed sequence tags in young roots of tea (Camellia assamica)

Assam tea (Camellia assamica) is perennial crop susceptible to moisture stress. We used its tender roots to construct a cDNA library for the identification, functional annotation, and analysis of transcripts. A total of 811 full-length expressed sequence tags were generated. After processing and assembly, 207 unigenes comprising 58 contigs and 149 singletons were registered. Finally, 35.75 % of the unigenes could be assigned to functional categories based on the Arabidopsis proteome. There was 43 % of a coding GC content and 1 272 coding DNA sequences found in the unigenes. Codon usage analysis shows leucine as the highest (9.92 %) and tryptophan (2.0 %) as the lowest coded amino acids. Further, a comparative study with drought-induced genes of young roots (reported earlier) reveals that 4.83 % of genes required for normal growth of roots were also induced by a drought stress. Expressions of 10 unigenes under different abiotic stresses, such as drought, cold, and salinity, were further confirmed by RT-qPCR. The sequence tags generated in this study will be valuable resources for functional genomics study of tea and other woody crop plants in future.

Insights of Transcriptomic Study of Tea

Tea (Camellia sinensis (L.) O. Kuntze), an evergreen cash crop, is indigenous to Indo-China region. These perennial shrubs intermittently encounter versatile stresses that impinge on production. However, tea consumption is escalating due to cheaper valuation. Hence, increased production entails appliance of advanced research and technological implications. Concurrently, complex life cycle and out-breeding nature of tea poses several inadequacies for genetic improvement. Abolition of winter dormancy, quicker flushes, and faster germination demands deliberation. Incidentally, efficacy of DNA based markers for molecular or genetic characterization has been exploited. Though, genome sequencing and advanced molecular approaches have made possible genome-wide analysis of changes molecular expression, creating the opportunity for studying biological processes. Nevertheless, solitary technology as a ‘stand-alone’ cannot be adequate for gaining a comprehensive understanding.