Boron and blue light reduce responsiveness of Arabidopsis hypocotyls to exogenous auxins

Abstract

We reported earlier that boron stimulates hypocotyl growth in several Arabidopsis ecotypes but not in the boron-deficient mutant bor1-1. Others have shown that boron influences the metabolism and transport of the plant hormone auxin. We investigated how boron, in interaction with light, influences Arabidopsis hypocotyl growth responses to the exogenous auxins 1-NAA, 2,4-D and IAA. In either light condition, 1-NAA similarly inhibited hypocotyl growth in bor1-1 and the corresponding WT (Col-0), while in both genotypes, boron did not essentially affect the extent of the inhibition. Whatever the light conditions and in the absence of boron, 2,4-D inhibited hypocotyl elongation in WT, while in BL seedlings, high responsiveness to 2,4-D vanished when boron was added to the culture medium. Hypocotyl of bor1-1 seedlings in all boron concentrations tested and grown in the dark or RL responded to the auxin similar to WT plants. In BL, the mutant hypocotyls retained full sensitivity to 2,4-D at 0.1 mM H 3 BO 3 but lost that sensitivity by 2 mM. In both genotypes tested, in the dark or RL, IAA inhibited hypocotyl growth. Conversely, IAA stimulated hypocotyl elongation in both genotypes developed in BL at 0.1 mM H 3 BO 3 . That stimulation disappeared when the boron supply increased to 2 mM. Our results suggest that specifically in BL, boron reduces hypocotyl responsiveness to auxins 2,4-D or IAA via the functional transporter BOR1. Our results lead to a discussion of how BL and BOR1 influence the mechanisms of auxin transport into and out of the cell.

Dynamic transcriptome and phytohormone profiling along the time of light exposure in the mesocotyl of rice seedling

“…A similar dosage of red light (60 s, 12 μmol/m 2 s) caused about 50% inhibition of mesocotyl growth in maize while a fluence of 1 mol/m 2 decreased the growth rate to about 20% of the dark control 25 . Other experiments observed the quantitative inhibition of mesocotyl elongation of maize seedlings 9 , 26 , 27 or hypocotyl growth of Arabidopsis seedlings 28 . So the mesocotyl growth in rice is more sensitive to light exposure than that in maize or the hypocotyl growth in Arabidopsis.…”

“…HY5 was 15 to 20 times more abundant in Arabidopsis seedlings grown in the light than in the dark and involved in the inhibition of hypocotyl elongation by light exposure 24 , 34 . Plants can perceive light through several kinds of photoreceptors, such as the phytochromes (phys), which absorb red/far-red light 10 , 11 , 16 , and the cryptochromes (crys), which absorb blue light 28 , 35 . The expression of PHY and CRY gene families did not change significantly in this study.…”

Interkingdom Hormonal Regulations between Plants and Animals Provide New Insight into Food Safety

“…It has versatile signaling pathway, acting as a general coordinator of plant growth and development, transferring information over both long and short ranges . The concentrations of IAA reported in field are about 0.05–100 μM. − …”