Plants are sessile in nature, therefore, they are exposed to various abiotic and biotic stresses, such as drought, chilling injury, insects, and diseases attack. Pubescence in plants offers the opportunity for them to withstand a number of stresses. Trichomes which are the epidermal outgrowths with single-cell or multicellular structures, cover most aerial plant tissues and are present in the enormous number of plant species. They play a vital role in plant growth and development, by protecting against herbivore attacks and pathogens, acting as a shield against damaging ultraviolet (UV) radiation and preventing excessive transpiration, and so on.2

Plant trichome development generally includes three stages: (1) fate determination and initiation, (2) branching, and (3) elongation and maturation. Many studies have confirmed that different transcription factor families, such as HD-ZIP type proteins, C2H2 zinc finger proteins, basic helix-loop-helix (bHLH) type proteins, and v-myb avian myeloblastosis viral oncogene homolog (MYB) family proteins, all play a key role in plant trichome development. In addition, trichome development is strictly regulated by a variety of plant hormones.1

Non glandular trichomes play a crucial role in managing abiotic stress through various adaptations. They contribute to drought resistance by lowering the transpiration rate, reflecting sunlight, storing water and regulating leaf temperature. In the context of salt resistance, these trichome sequester salt, enhance water retention and neutralize reactive oxygen species (ROS) activity. Dense trichomes could also present a physical barrier to movement of microorganisms and feeding of insects, thus protecting plants against biotic stresses. Glandular trichomes resist the insects and pathogens by synthesizing and storing defensive chemicals like phenols, flavonoids, methyl ketones, acyl sugars and terpenoids.1

A study examined the role of trichomes on tomato plants in protecting against stresses like disease, pests, drought, and cold damage. Four tomato varieties (3186 M, 3186 L, LA 3-071, JR) with different trichome densities and types were analyzed to understand the relationship between trichomes and stress resistance, aiming to improve tomato breeding and cultivation.3 Another study on soybean identified nine QTLs associated with trichome density while ten QTLs for trichome length, finding that wild soybean had alleles for decreased length and increased density. The study also identified candidate genes for the traits and found that leaves with short, dense pubescence (like wild soybean) were most resistant to common cutworm, providing insights for breeding more resilient soybeans.2

SELECTED REFERENCES:

1HAN, G., LI, Y., YANG, Z., WANG, C., ZHANG, Y. AND WANG, B., 2022, Molecular mechanisms of plant trichome development. Front. Plant Sci., 13: 9102.

2LI, Y., CHU, L., LIU, X., ZHANG, N., XU, Y., KARIKARI, B., WANG, Y., CHANG, F., LIU, Z., TAN, L. AND YUE, H., 2022, Genetic architecture and candidate genes for pubescence length and density and its relationship with resistance to common cutworm in Soybean. Front. Plant Sci., 12: 771850.

3ZHANG, Y., SONG, H., WANG, X., ZHOU, X., ZHANG, K., CHEN, X., LIU, J., HAN, J. AND WANG, A., 2020, The roles of different types of trichomes in tomato resistance to cold, drought, whiteflies, and botrytis. Agronomy, 10(3): 411.