Effects of exogenous 5-aminolevulinic acid on photosynthesis, stomatal conductance, transpiration rate, and PIP gene expression of tomato seedlings subject to salinity stress

Abstract

ABSTRACT. The effects of exogenous 5-aminolevulinic acid (ALA) on photosynthesis, plant growth, and the expression of two aquaporin genes in tomato seedlings under control and salinity conditions were investigated. Exogenous ALA application significantly improved net photosynthetic rate (P n ), total chlorophyll content, and plant biomass accumulation of tomato seedlings under salinity stress. As revealed by real-time PCR analyses, after treatment with ALA alone, expression of both LePIP1 and LePIP2 in the two tomato cultivars was upregulated at 2 h and subsequently decreased to normal levels. Under salinity stress, transcript levels of LePIP1 in both leaves and roots of salt-sensitive cultivars (cv. Zhongza No.9) increased significantly and were considerably higher than in cultivars exposed to ALA alone. In contrast, the expression levels of LePIP1 and LePIP2 in cvs. Jinpeng No.1 cultivars were slightly lower under salinity stress than under ALA treatment. In addition, transcript levels of both LePIP1 and LePIP2 in the roots of Jinpeng No. 1 cultivars were considerably lower than those Y.Y. Zhao et al. 6402©FUNPEC-RP www.funpecrp.com.br Genetics and Molecular Research 14 (2): 6401-6412 (2015) in the roots of Zhongza No. 9 cultivars under salinity stress, regardless of ALA supplementation, implying that Jinpeng No. 1 cultivars had a better capacity to maintain membrane intrinsic protein stability. Further, ALA application distinctly counteracted the up-or down-regulation of LePIP1 and LePIP2 in both cultivars under salinity stress, in accordance with the improvements instomatal conductance, transpiration rate, and P n of tomato leaves. The results presented here indicate that ALA controls aquaporin expression, thus, presumably ALA regulates water homeostasis and enhances salt tolerance of tomato seedlings.

Overexpression of calmodulin-like (ShCML44) stress-responsive gene from Solanum habrochaites enhances tolerance to multiple abiotic stresses

“…Leaf water-retention capacity is strongly related to the stomatal conductance and transpiration rate in plants4950. Under stress conditions, our results indicated significantly higher stomatal conductance and transpiration rate in ShCML44 overexpressing lines than that of wild-type plants (Figs 5b,d and 8b,d).…”

“…Stomatal conductance and transpiration rate contribute to improving photosynthesis and intercellular CO 2 concentration rate51, our findings demonstrated significantly higher activity of photosynthesis and intercellular CO 2 rate in transgenic plants compared to wild-type in stress conditions (Figs 5a,c and 8a,c). Furthermore, higher gas exchange attributes play a critical role to improve relative water content by higher root water uptake50. Under drought conditions, our findings showed lower leaf water loss rate and improved RWC in transgenic plants than the wild-type (Fig.…”

“…To determine the gas exchange attributes and measure the photosynthetic system under cold stress, two months old plants were exposed to cold stress for one week and the total chlorophyll, photosynthetic rate (A), transpiration rate (E), intercellular CO 2 concentration rate and stomatal conductance (gs) were measured. The detailed methodology for the measurements of gas exchange attributes and total chlorophyll content is described in Zhao et al 50.…”

The iTRAQ-based chloroplast proteomic analysis of Triticum aestivum L. leaves subjected to drought stress and 5-aminolevulinic acid alleviation reveals several proteins involved in the protection of photosynthesis

“…Because of the predominantly protective effect of ALA against environmental stress, its mechanism has increasingly gained attention. According to the existing evidence, the exogenous application of ALA increases the chlorophyll content, activates antioxidant enzymes, reduces lipid peroxidation of the membrane [13], promotes photosynthesis [15], enhances the tetrapyrrole biosynthetic pathway and proline accumulation [14], improves the metabolism of polyamines [17], regulates nitrogen metabolism, absorption, aggregation and distribution of nutrient ions [22,25], inhibits the microstructural damage in chloroplasts by increasing the proportion of intact thylakoids [26], and regulates the expression of genes [27]. Our previous study showed that ALA pretreatment enhanced the photosynthetic capacity of droughtstressed wheat seedlings [23], but the regulatory mechanism behind this effect is still unknown.…”

5-Aminolevulinic acid (ALA) promotes primary root elongation through modulation of auxin transport in Arabidopsis

“…ALA also improved root growth of cucumber (Cucumis sativus L.) (Zhen et al 2012), Swiss chard (Beta vulgaris L. subsp. cicla) (Liu et al 2014), rice (Oryza sativa) (Nunkaew et al 2014), and tomato (Solanum lycopersicum) (Zhao et al 2015) seedlings under NaCl stress. Moreover, ALA enhanced root growth of spring wheat (Triticum aestivum L.) (Kosar et al 2015), oilseed rape (Brassica napus L.) (Liu et al 2016), and Arabidopsis (An et al 2016c) under water deficit condition.…”