Modification of phytosterol composition influences cotton fiber cell elongation and secondary cell wall deposition

Abstract

Background Cotton fiber is a single cell that arises from the epidermis of ovule. It is not only a main economic product of cotton, but an ideal material for studying on the growth and development of plant cell. Our previous study indicated that phytosterol content and the ratio of campesterol to sitosterol fluctuated regularly in cotton fiber development. However, what effects of modified phytosterol content and composition on the growth and development of cotton fiber cell is unknown. In this study, we overexpressed the GhSMT2–1 , a cotton homologue of sterol C-24 methyltransferase 2 gene in transgenic upland cotton plants to modify phytosterol content and composition in fiber cells and investigated the changes on fiber elongation and secondary cell wall deposition. Results GhSMT2–1 overexpression led to changes of phytosterol content and the ratio of campesterol to sitosterol in fiber cell. At the rapid elongation stage of fiber cell, total phytosterol and sitosterol contents were increased while campesterol content was decreased in transgenic fibers when compared to control fibers. Accordingly, the ratio of campesterol to sitosterol declined strikingly. Simultaneously, the transgenic fibers were shorter and thicker than control fibers. Exogenous application of sitosterol or campesterol separately inhibited control fiber cell elongation in cotton ovule culture system in vitro. In addition, campesterol treatment partially rescued transgenic fiber elongation. Conclusion These results elucidated that modification of phytosterol content and composition influenced fiber cell elongation and secondary cell wall formation. High sitosterol or low ratio of campesterol to sitosterol suppresses fiber elongation and/or promote secondary cell wall deposition. The roles of sitosterol and campesterol were discussed in fiber cell development. There might be a specific ratio of campesterol to sitosterol in different developmental stage of cotton fibers, in which GhSMT2–1 play an important role. Our study, at a certain degree, provides novel insights into the regulatory mechanisms of fiber cell development. Electronic supplementary material The online version of this article (10.1186/s12870-019-1830-y) contains supplementary material, which is available to authorized users.

Advances about the Roles of Membranes in Cotton Fiber Development

“…In addition, campesterol treatment partially rescued transgenic fiber elongation. There might be a specific ratio of campesterol to sitosterol in different developmental stages of cotton fibers, in which GhSMT2-1 plays an important role [ 33 ].…”

Fumonisin B1-Induced Changes in Cotton Fiber Elongation Revealed by Sphingolipidomics and Proteomics

“…Sphingolipids and sterols are important components of cell membranes, and play important roles in the regulation of membrane fluidity, permeability, and membrane-binding protein activity [ 5 , 6 , 7 ]. As phytosterols (especially sitosterol) have higher fiber elongation stage and lower fiber secondary cell wall deposition stage, changes in sterol content and composition affect fiber cell development [ 8 ]. Although phytosterols play important roles in fiber development, the role of sphingolipids in this process is not clear.…”

Comparative Metabolomics Analysis Reveals Sterols and Sphingolipids Play a Role in Cotton Fiber Cell Initiation

“…Phytosterols have structural and functional roles in plant growth and development [ 49 , 50 ], and its role in numerous physiological processes is well established, such as cell division, cell elongation, vascular element development, and tolerance to abiotic and/or biotic stress [ 50 , 51 , 52 ]. Phytosterols also play vital roles in ovule growth and fiber elongation in cotton [ 41 , 53 , 54 , 55 ]. However, the role of sterols in the differentiation and initiation of fiber cell is still unclear.…”

“…It is considered that the ratio of campesterol to sitosterol (C/S) is an important factor affecting plant growth and development [ 40 ]. During the growth and development of cotton fiber cells, the ratio of C/S changed greatly in different developmental stages, such as elongation period (primary wall synthesis stage) present higher C/S value and secondary wall synthesis stage present lower C/S value [ 41 , 53 ]. In the study, the content of sitosterol has no significant difference between the two mutants and wild-type, while the content of campesterol was significantly higher in the two mutants, resulting in a significant increase in the C/S value ( Figure 3 B).…”