Rice calli may decelerate its metabolism to adapt hormone free medium
2021
Jin, Jing | Essemine, Jemaa | Duan, Jianli | Zhu, Jian | Cai, Weiming
This report focuses on the crucial role of lipids and starch metabolism in the growth and ultrastructure of the cell wall (CW) in rice calli. Non-habituated calli (NH-calli) were isolated from a rice embryo-derived callus culture supplemented with 2,4-D (2,4-Dichlorophenoxyacetic acid); however, the habituated calli (H-calli) were isolated from NH ones and cultured subsequently on exogenous hormone-free medium. The phenotypes of the H- and NH-calli differed significantly between each other as reported in our recently published work. The H-calli CW was thinner, the endoplasmic reticulum (ER), mitochondria (MT) and starch grains (SGs) were less in the H-calli. The intracellular free fatty acids (FAs) and starch content were much less in the H- if compared to NH-calli. By microarray analysis, the differentially expressed genes (DEGs) related to primary and secondary metabolism, lipid and starch metabolism were down-regulated in H- vs NH-calli. The response at the transcriptomic level involved in these changes, as well as the corresponding variations in cytology and FAs metabolism were also accurately elucidated herein. The study reveals that the decreased levels of lipids and starch in the H-calli are mainly attributable to their (H-calli) elevated consumption, in the absence of exogenous hormonal supply to ensure the demand in energy of the calli to survive and maintain an optimum growth and development with the available resource of energy (starch and lipids). This report displays as well the slowdown of the H-calli metabolism, in the absence of exogenous growth regulators supply, if compared to that of the NH-ones.
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