Small heat shock proteins (sHSPs) function as molecular chaperones, which play crucial roles in plant growth, development, and stress response. However, the function of the sHSP gene in the tea plant (Camellia sinensis L.) has not been extensively investigated. In total, 54 C. Sinensis small heat shock proteins (CssHSPs) in the tea plant genome were screened. Phylogenetic analysis revealed that CssHSPs in the same group have similar conserved domains and motifs; conversely, significant structural differences exist in the different groups. Most CssHSP genes had tissue-specific expression. They also responded to one or more abiotic or biotic stresses, CsHSP24.6 was selected for functional analysis. The results demonstrated that the expression of CsHSP24.6 increased under abiotic stresses such as temperature, light intensity, and NaCl. In addition, under high temperature and high light intensity treatments, CsHSP24.6 and its target gene CspTAC5 interacted to enhance the heat and light resistances of the plant. CsHSP24.6 facilitates resistance to abiotic stresses in tea plants. These results further support that CsHSP24.6 plays an essential role in maintaining plant growth and development under abiotic stress.

Tea is the second most consumed non-alcoholic beverage, only next to water. However, its production and qualities, including rich flavors and numerous health benefits, are often degraded by environmental stresses and contaminations with various agrochemicals. While most of tea quility-contributing secondary metabolites are synthesized in tea plant leaves, such as catechins, caffeine, volatiles, saponins, and theanine, primarily for defenses against biotic and abiotic stresses, few tea garden management measures have employed this tea plant innate innumity to enhance their tolerance against environmental stresses. This is partly due to the limited understanding of the biosynthesis and regulationof tea plant secondary metabolism. Given the importance of tea plant secondary metabolites for both tea flavors, health functions, and resistance against environmental stresses, study and in-depth understanding of the biosynthesis and environmental regulation of tea plant specialized metabolites are highly expected. Strategies developed from these studies would promote the production of safe and high quality teas. The review highlights relevant contexts of tea plant-environmental interaction at the secondary metabolism interfaces, particular their roles in enhancement of tea plant innate immunity and tea quality, so as to guide future research on genetic improvement of tea plants for safer food production and better human nutrition.