Altered tetrapyrrole metabolism and transcriptome during growth-promoting actions in rice plants treated with 5-aminolevulinic acid

Abstract

As a precursor of chlorophyll, 5-aminolevulinic acid (ALA) acts as a growth-promoting factor in plants, but little is known of molecular basis of plant growth action. The exogenous supply of an optimal concentration of 75 lM ALA without photooxidative risks, as indicated by a negligible change in conductivity, increased dry shoot biomass of rice up to 16 % after 10 days of ALA treatment, compared to the untreated control. Although rice plants treated with ALA gradually increased levels of ALA-synthesizing capacity during 30 h of the treatment, a noticeable increase in chlorophyll content was not observed. Levels of protoporphyrin IX and Mg-porphyrins were not significantly changed 6 h after ALA treatment and then decreased 30 h after the treatment, while transcript levels of most biosynthetic genes in tetrapyrrole pathway almost kept constant or slightly decreased. In microarray analysis of ALA-treated rice plants, categories of significantly upregulated transcripts highlight particular biological processes involved in cell cycle, transcription factors, posttranscriptional regulation, and metabolisms of macromolecules. Our results demonstrate that the regulation of tetrapyrrole biosynthesis did not contribute significantly to growth enhancement in ALA-treated rice. We propose that the elevated status of ALA in plant cells alters the transcriptional control of genes involved in physiological processes vital for plant growth, thereby contributing to enhancement of plant biomass.

5-Aminolevulinic acid (ALA) biosynthetic and metabolic pathways and its role in higher plants: a review

“…Proved by research in the chlorophyll-deficient mutant of Chlamydomonas reinhardtii, the levels of mRNA and protein output of ChlH are both increased while ChlI and ChlD remained unalterable from dark condition to light (Chekounova et al 2001). Then, Mg-protoporphyrin IX methyltransferase (MgMT) devolves a methyl group from S-adenosyll-methionine to Mg-Proto IX, giving Mg-protoporphyrin IX monomethyl ester (Mg-Proto IX ME) (Nguyen et al 2016). Followed by Mg-protoporphyrin IX monomethyl ester cyclase (MgCy), the reaction merges atomic oxygen (O) to Mg-Proto IX ME and creates 3,8-divinyl protochlorophyllide.…”

5-Aminolevulinic Acid (ALA) Alleviated Salinity Stress in Cucumber Seedlings by Enhancing Chlorophyll Synthesis Pathway

“…Therefore, photosynthetic capacity of photosystems II (PS II) was enhanced by increasing light-harvesting pigments in our study. Exogenous ALA increased the content of chlorophyll in rice ( Oryza sativa L.) ( Nguyen et al, 2016 ). Subsequently, we also noticed that at stressful condition, heme content and HEMH expression were not reduced to the level of CK.…”

“…5-aminolevulinic acid (ALA) has been considered as a growth regulator or potential plant hormone in higher plants. Its promotive role in enhancing plant biomass, photosynthesis and fruit quality under normal growth condition has been confirmed in rice ( Oryza sativa L.) ( Nguyen et al, 2016 ), strawberry ( Fragaria ananassa Duch.) ( Sun et al, 2017 ), and peach ( Prunus persica L.)( Ye et al, 2017 ).…”

Hydrogen peroxide as a mediator of 5‐aminolevulinic acid‐induced Na+ retention in roots for improving salt tolerance of strawberries

“…Zhang et al (, ) approved that either over‐production of endogenous ALA in YHem1 transgenic Arabidopsis or exogenous ALA treatment in tomato seedlings resulted in more heme accumulation under salt stress. Recent reports on RNA‐seq have shown that the improvement of ALA in plant stress tolerance is associated with its own promotion of tetrapyrrole metabolism (Nguyen et al , Niu and Ma , Wu et al , Xiong et al ). Therefore, one or more components in ALA metabolic pathways may be involved in the regulation of plant tolerance against salt stress.…”

“…ALA has been found to induce antioxidant enzyme activities (Nishihara et al , Akram and Ashraf ), as well as nonenzymatic antioxidant substances, such as ascorbate, glutathione, proline and polyphenols, which are involved in the elimination of excess ROS and the prevention of oxidative stress (Wongkantrakorn et al , Al‐Ghamdi and Elansary ). Recently, several studies have emphasized that the mechanism of ALA‐improved plant stress tolerance is associated with the promotion of tetrapyrrole metabolism (Nguyen et al , Niu and Ma , Wu et al , Xiong et al ). These are in agreement with our previous study, where Wang et al () found that the germination of pak choi seeds, promoted by ALA under salinity, depended on its conversion into tetrapyrroles.…”