Influence of 5-aminolevulinic acid on photosynthetically related parameters and gene expression in Brassica napus L. under drought stress

Abstract

In the present study, the roles of foliarly applied 5-aminolevulinic acid (ALA) in photosynthetic parameters, ion contents and expression of several photosynthetic genes were investigated in rapeseed (Brassica napus L.) under well watered and drought conditions. Drought stress reduced relative plant growth rate and leaf water content (RWC), and contents of photosynthetic pigments, starch, soluble proteins and ions in roots. This type of stress, however, stimulated the accumulation of soluble sugars and free amino acids, as well as leaf proline contents. The transcript levels of photosynthetic genes were also down-regulated under drought stress. Exogenously applied ALA partially reduced growth inhibition and increased RWC and chlorophyll contents under drought conditions. The expression of photosynthetic genes was induced by ALA under both normal and drought conditions, which may contribute to an increased photosynthetic capacity. The ALA application further improved the accumulation of hexose and sucrose, accompanied by the maintenance of starch contents in the leaves and possibly relatively higher RWC under drought stress. Based on these results, we suggest that ALA promotes plant growth under drought stress via improving photosynthetic assimilation, increasing chlorophyll content and inducing the expression of several photosynthetic genes. ARTICLE HISTORY

Substrate Application of 5-Aminolevulinic Acid Enhanced Low-temperature and Weak-light Stress Tolerance in Cucumber (Cucumis sativus L.)

“…ALA is a vital precursor of the tetrapyrrole biosynthesis pathway, and is considered to be a plant growth regulator and to regulate plant defense mechanisms to mitigate the harmful effects of abiotic stress [9,10]. As reported previously, low temperature has adverse impacts on cucumber seedlings, and results in a significant reduction in Chl accumulation and photosynthetic capacity [12,13]. Exogenous ALA application is involved in regulation of endogenous hormones, chlorophyll and nutrient accumulation, and the plant defense system, and significantly reduces the harmful effects of low temperature and improves cucumber seedling growth [10].…”

“…In tomato plants, plasma membrane intrinsic proteins (PIPs) genes, such as PIP1 and PIP2, are regulated by exogenous ALA treatment. ALA not only enhances salinity stress tolerance, but also stimulates chlorophyll accumulation, chlorophyll fluorescence, and photosynthetic capacity [13]. In our previous study, we reported that exogenous ALA increases endogenous hormone accumulation, especially of 24-epibrassinolide, which regulates plant defense mechanisms, photosynthesis-related enzymes (such as Rubisco) and increasing the expression level of rca, rbcS, and rbcl involved in photosynthesis [27][28][29].…”

“…These findings indicate that ALA reduced the toxic effects of low-temperature and weak-light stress. ALA regulates photosynthesis-related parameters and transcript levels of RBCS, TPI, FBP, fructose-1,6-bisphosphate aldolase, and transketolase under drought stress in rapeseed plants [13]. In tomato plants, plasma membrane intrinsic proteins (PIPs) genes, such as PIP1 and PIP2, are regulated by exogenous ALA treatment.…”

“…Transcriptome analysis suggested that photosystem II oxygen-evolving enhancer protein, photosystem I subunit, light-harvesting chlorophyll protein complex I and II, ferredoxin, P n , T r , ΦPSII, ETR, and qP, are upregulated under ALA treatment [25]. ALA is a crucial precursor in the biosynthesis of all porphyrin compounds, such as chlorophyll, heme, and phytohormones [8,12,13]. These findings indicated that exogenous ALA application stimulated the biosynthesis pathway, that enhanced chlorophyll (Figure 3), photosynthetic capacity (Figure 4), and chlorophyll fluorescence (Table 1), and reduced the detrimental effects of low-temperature and weak-light stress.…”

“…Exogenous ALA application increases chlorophyll accumulation and chlorophyll fluorescence indices in lettuce and oilseed rape [11,12]. It has recently been reported that ALA regulates the expression level of fructose-1,6-bisphosphatase (FBP), triose-3-phosphate isomerase (TPI), and ribulose-1,5-bisphosphate carboxylase/oxygenase small subunit (RBCS), which activate the Calvin cycle of photosynthesis under drought stress [13]. In a previous study we observed that ALA regulates endogenous hormone and nutrient accumulation in cucumber to induce low-temperature stress tolerance [10].…”