Classification of fruit trichomes in cucumber and effects of plant hormones on type II fruit trichome development

Authors: XUE, SD - China Agricultural University; DONG, MM - China Agricultural University; LIU, XW - China Agricultural University; XU, S - China Agricultural University; PANG, JN - China Agricultural University; ZHANG, WZ - China Agricultural University; Weng, Yiqun; REN, HZ - China Agricultural University

Submitted to: Planta
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/3/2018
Publication Date: 9/17/2018
Citation: Xue, S., Dong, M., Liu, X., Xu, S., Pang, J., Zhang, W., Weng, Y., Ren, H. 2018. Classification of fruit trichomes in cucumber and effects of plant hormones on type II fruit trichome development. Planta. 249:407-416. https://doi.org/10.1007/s00425-018-3004-9.
DOI: https://doi.org/10.1007/s00425-018-3004-9

Interpretive Summary: The fruit spines (trichomes) of cucumber are a specialized structure derived from the epidermal cells with very diverse morphology. Fruit spines grow perpendicular to the fruit surface. Cucumber fruit spine is an important fruit quality trait. Cucumbers from different market classes are different in spine size, and density. To understand the underlying molecular mechanism of fruit trichome development, in this study, we conducted morphological characterization and classification of cucumber fruit spines and their developmental processes. We examined the fruit spines among 200 cucumber varieties, and found their spines could be classified into eight morphologically distinct types (I to VIII). There are two main developmental patterns of the eight types of spines. The development of glandular trichomes had multiple stages including initiation and expansion of the trichome precursor cell followed by periclinal bipartition to two cells (top and bottom) which later formed the head region and the stalk, respectively through subsequent cell divisions. The non-glandular trichome development started with expansion of the precursor cell perpendicularly to the epidermal plane followed by cell periclinal division to form a stalk comprising of some rectangle cells and a pointed apex cell; then the base cell started anticlinal bipartition to two cells, which then underwent many cell divisions to form a multicellular spherical structure. In addition, plant hormones are closely related to trichome development. We found that GA and BAP were capable of increasing trichome number per fruit with distinct effects under different concentrations. Results from this study provide new insights into cucumber fruit spine organogenesis, which will be helpful in better understanding of the molecular mechanisms of spine development in cucumber. This knowledge may also be useful for cucumber breeders in developing varieties for different market classes.

Technical Abstract: The fruit trichomes or fruit spines of cucumber, Cucumis sativus L, are highly specialized structures originating from epidermal cells with diverse morphology, which grow perpendicular to the fruit surface. To understand the underlying molecular mechanisms of fruit trichome development, in this study, we conducted morphological characterization and classification of cucumber fruit spines and their developmental processes. We examined the fruit trichomes among 200 cucumber varieties, which could be classified into eight morphologically distinct types (I to VIII). Investigation of the organogenesis of the eight types of trichomes revealed two main developmental patterns. The development of glandular trichomes had multiple stages including initiation and expansion of the trichome precursor cell which protuberating out of the epidermal surface, followed by periclinal bipartition to two cells (top and bottom) which later formed the head region and the stalk, respectively through subsequent cell divisions. The non-glandular trichome development started with expansion of the precursor cell perpendicularly to the epidermal plane followed by cell periclinal division to form a stalk comprising of some rectangle cells and a pointed apex cell; then the base cell started anticlinal bipartition to two cells, which then underwent many cell divisions to form a multicellular spherical structure. In addition, phytohormones as environmental cues were closely related to trichome development. We found that GA and BAP were capable of increasing trichome number per fruit with distinct effects under different concentrations.