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

Abstract

The specific function of 5-aminolevulinic acid (ALA), a new plant growth regulator, in modulating root growth of plants and the mechanisms underlying ALA-regulated root growth are largely unknown. Here, Arabidopsis seedlings were photographed and collected before and after ALA or 2,3,5-triiodobenzoic acid (TIBA) treatment for determination of root growth, fluorescence intensities of PIN1, PIN2, PIN7, and DR5, and gene expression levels of auxin synthesis, signaling, and transport. We first demonstrated that ALA significantly promoted Arabidopsis primary root elongation. We also found that TIBA, an auxin polar transport inhibitor, inhibited ALA-promoted root elongation, indicating that auxin transport is involved in ALAregulated root growth. Then, the observations of PIN1, PIN2, and PIN7 at protein and transcript levels suggest that ALA improves auxin transport mainly through regulating auxin efflux carriers. Furthermore, the expression patterns of auxinresponsive reporter DR5rev:GFP were not correlated well with the expression of YUC2, a key biosynthetic gene of auxin, but were consistent with changes of PIN1, PIN2, and PIN7. In addition, ALA did not affect the gene expression of auxin receptor, TRANSPORT-INHIBITOR-RESISTANT1 (TIR1). Taken together, we conclude that ALA promotes primary root elongation of young Arabidopsis seedlings mainly through improving auxin transport. Our data suggest the reciprocal interaction between ALA and auxin, providing new insights into the mechanisms underlying ALA-promoted plant root growth. Keywords 5-Aminolevulinic acid • Arabidopsis • Auxin • Polar transport • Root growth Communicated by B. Zheng. Yuyan An and Danxuan Cheng contributed equally to this work.

5-Aminolevulinic Acid and 24-Epibrassinolide Improve the Drought Stress Resilience and Productivity of Banana Plants

“…The application of ALA also improved the total and reducing sugars, fruit weight and volume, and flesh percentage in date palm [ 106 ]. This improvement in plant growth and productivity is generally associated with all pathways involved in root growth (particularly the mechanism of auxin transport and biosynthesis) [ 107 ], chlorophyll biosynthesis, and total chlorophyll content [ 33 ], which are associated with improved yield and fruit quality ( Table 3 , and Figure 4 and Figure 5 ) due to an increased photosynthetic rate [ 14 ]. It was reported that ALA inhibits ABA-induced stomatal closure via the reduction of the H 2 O 2 and Ca 2+ levels in guard cells and simultaneously improves the photosynthesis of stressed plants [ 108 ].…”

“…Both PIN1 and PIN7 mainly regulate acropetal auxin transport, while PIN2 specifically influences the basipetal auxin transport [ 111 , 112 ]. An et al [ 107 ] reported that ALA regulates PIN proteins at both the transcriptional and post-transcriptional levels and its effect on root growth in a concentration-dependent manner. Low concentrations (e.g., 10 mg·L −1 ) improved root elongation, while higher concentrations (e.g., 20 mg·L −1 ) inhibited it but stimulated the initiation of lateral roots.…”

PP2A and microtubules function in 5‐aminolevulinic acid‐mediated H2O2 signaling in Arabidopsis guard cells

“…RCN1, one of the three PP2A scaffolding subunits in Arabidopsis (Deruere et al ), positively functioned in MeJA‐as well as ABA‐induced stomatal closure (Kwak et al , Saito et al ), further demonstrating a role of PP2A in guard cell signaling. ALA showed a broad crosstalk with other plant growth regulator, including ABA (An et al ), BR (Zheng et al ), auxin (An et al ) and ethylene (An YY, Hu S and Wang LJ unpublished data). In light of these reports, we speculate that PP2A may also participate in ALA signaling, including ALA‐regulated stomatal movement.…”

Advances in 5-Aminolevulinic Acid Priming to Enhance Plant Tolerance to Abiotic Stress

“…ALA is a growth regulator that regulates the growth and development of plants at different growth stages. Soaking seeds with ALA reduces the germination time and increases the germination index of pigeon pea, and promotes Arabidopsis thaliana root elongation by regulating auxin transport [ 8 , 72 ]. ALA significantly increased yields through root or foliar fertilization in grapevines ( Vitis vinifera ) [ 73 ].…”