Primary Metabolism and Transcriptional Regulation in Higher Plants

Abstract

Metabolism, which is a flow of metabolites, is orchestrated by gene expression, and it is in turn regulated by metabolites. Some of the metabolites are known to act as signaling molecules that regulate metabolism and also developmental processes in plants. Here we summarize findings about metabolites-directed gene regulation, focusing on primary metabolites including sugars and organic acids. Abundant soluble sugars such as sucrose and glucose are known to induce genes involved in starch storage, synthesis and degradation. These sugars also activate anthocyanin biosynthesis and suppress photosynthetic genes, both of which promote photoprotection responses. Several kinases, like hexokinase, sucrose non-fermenting1-related kinase 1 and target of rapamycin kinase have been identified, which are the major regulators of transcriptional regulation by these sugars. Although less studied than sugars, metabolites constituting the TCA cycle are good candidates of signaling molecules, because they are located in the primary metabolism adjacent to the respiratory electron transport system and thus are reflected by both primary metabolism and redox status of the electron transport system. Some organic acids as citrate, malate and 2-oxoglutarate have also been known to be implicated in the regulation of gene expression. Deficiency or over accumulation of some primary metabolites not only modulate gene expression of the local metabolic enzymes to supplement distorted metabolism but produce signals to balance between bigger metabolic blocks like carbon and nitrogen metabolisms. Status of primary metabolites can also produce signals of overall energy levels of plants. Relationship of sugar signaling to reactive oxygen species signaling is also suggested.

The secretory scales and medicinal properties of combretum erythrophyllum.

“…Medicinal properties are attributed to secondary metabolites found in certain plant species (A'attiyyah et al, 2018(A'attiyyah et al, , Bantho et al, 2020. Synthesized primary metabolites are crucial to cell functioning Hayami et al, 2021). These compounds play important roles in growth and development, whilst secondary metabolites are plant specific and are produced as part of the plant defence system against pests and pathogens , Pang et al, 2021.…”

“…Trichomes are minute protuberances from the leaf epidermis and are said to be the site of synthesis as well as the reservoir of accumulated biological substances Hayami et al, 2021). Trichomes range from simple hairs to specialized tissues with varying functions and may be widely spread across both the vegetative and reproductive parts of the plant .…”

“…Non-glandular trichomes can be found in abundance on foliar surfaces yet may differ in structure and function Hayami et al, 2021). They are categorised as unicellular or multicellular structures, that are either simple, branched or starred (Xiang et al, 2010).…”

“…Within plant species, there are two structurally and functionally defined metabolite groups (McGaw and Eloff, 2008;Ahman et al, 2018;Panchawat et al, 2021). Primary metabolites comprising of amino acids, nucleic acids, and sugars, are essential to cellular development, functioning, and reproduction Hayami et al, 2021). While exuded secondary metabolites are crucial to plant defence and include metabolites such as phenols, tannins, alkaloids, saponins, and other such organic metabolites (Ascensão and Pais, 1987;.…”

“…CHAPTER 2: LITERATURE REVIEW Secretory tissues are found in abundance upon foliar surfaces (Barthlott et al, 2017). The variation amongst morphology, exudate and function of secretory tissues are used to classify and distinguish between tissue types and classes Hayami et al, 2021). highlighted the structural differences between secretory tissues that occur in plants, ranging from single cells to complex multicellular structures.…”