Exploring the role of auxin in the androgynophore movement in Passiflora

et al. 2022

Preprint

Madeira vine (MV) grows 30 times faster after encountering a support. In vivo x-ray diffraction made on live MV stems revel the appearance of crystallized IAA (C10H9NO2), 4-Cl-IAA (C10H8ClNO2) and 6-Cl-IAA (C10H8ClNO2) in the stems. Small angle neutron scattering spectra of the IAA extracted from MVs stem reveal a progressive increase in the size of crystallized IAA transported downward from the apex of the shoots. High resolution X-ray diffractions made on the extracted IAA reveal significantly larger amounts of 4-Cl-IAA and 6-Cl-IAA in the climbing MVs than in the swaying around MVs. The gas chromatography-mass spectrometry spectra reveal the production of 9% more IAA and 90% more 4-Cl-IAA+6-Cl-IAA at the apexes of climbing MVs than swaying MVs. More 4-Cl-IAA+6-Cl-IAA were transported to the contact-free side than to the contact side of the vine. In vivo neutron tomography of naturally climbing MVs reveals a substantially higher H+ concentration in the contact-free parts than in the contact parts. The absorption spectra also reveal more expansin in the contact-free parts than in the contact parts. These results provide a view, at the molecular level, of what triggers the faster and differential growths in MVs in response to touching a support.

Section: Resultsmentioning

confidence: 99%

Enhanced expression of 4-Cl-IAA and 6-Cl-IAA by touch stimulus for rapid and differential growths of the Madeira vine

et al. 2022

Preprint

“…Three naturally occurring active auxins, indole-3-acetic acid (IAA, C 10 H 9 NO 2 ), 4-chloroindole-3-acetic acid (4-Cl-IAA, C 10 H 8 ClNO 2 ), and phenylacetic acid (PAA, C 8 H 8 O 2 ), have been identi ed in plant [18]. Among them, IAA is the most frequently found active auxin and has been recognized to be the key ingredient for cell enlargement and division in plants [19][20], participating directly in all tropism responses [20][21]. 4-Cl-IAA is a chlorinated analogue of IAA.…”

Section: Faster Growthmentioning

confidence: 99%

Halogenation of IAA by touch stimulus for rapid and differential growths of the Madeira vine

et al. 2023

Preprint

Background The thigmotropic response triggers two actions of faster growth and differential growth. Madeira vine (MV) grows 30 times faster after encountering a support. The question as to “how the vine can provide sufficient amounts of active auxin and effectively transport it into the cells for fast growth in such a short time” has not yet been answered.Results In vivo x-ray diffraction made on live MV stems revel the appearance of crystallized IAA (C10H9NO2), 4-Cl-IAA (C10H8ClNO2) and 6-Cl-IAA (C10H8ClNO2) in the stems. Small angle neutron scattering spectra of the IAA extracted from MVs stem reveal a progressive increase in the size of crystallized IAA transported downward from the apex of the shoots. High resolution X-ray diffractions made on the extracted IAA reveal significantly larger amounts of 4-Cl-IAA and 6-Cl-IAA in the climbing MVs than in the swaying around MVs. The gas chromatography-mass spectrometry spectra reveal the production of 9% more IAA and 90% more 4-Cl-IAA + 6-Cl-IAA at the apexes of climbing MVs than swaying MVs. More 4-Cl-IAA + 6-Cl-IAA were transported to the contact-free side than to the contact side of the vine. In vivo neutron tomography of naturally climbing MVs reveals a substantially higher H+ concentration in the contact-free parts than in the contact parts.Conclusions Enhanced expressions of auxin 4-Cl-IAA (C10H8ClNO2) and 6-Cl-IAA (C10H8ClNO2) through halogenation of IAA (C10H9NO2) triggered by the physical touch, rather than accumulation of auxin IAA, are the main sources to drive faster growth of Madeira vine. The IAA, 4-Cl-IAA and 6-Cl-IAA molecules produced in apex link into crystallized form, rather than stay in the molecular form, upon transporting downward to the stem.

“…Three naturally occurring active auxins have been identified in plants: indole‐3‐acetic acid (IAA, C 10 H 9 NO 2 ), 4‐chloroindole‐3‐acetic acid (4‐Cl‐IAA, C 10 H 8 ClNO 2 ), and phenylacetic acid (PAA, C 8 H 8 O 2 ). [ 2 ] Among them, IAA is the most frequently found active auxin, [ 3,4 ] participating directly in all tropism responses. [ 4,5 ] An IAA molecule consists of two benzenes and a carboxyl group, where the carboxyl group is weakly connected to the benzene group.…”

Section: Introductionmentioning

confidence: 99%

“…[ 2 ] Among them, IAA is the most frequently found active auxin, [ 3,4 ] participating directly in all tropism responses. [ 4,5 ] An IAA molecule consists of two benzenes and a carboxyl group, where the carboxyl group is weakly connected to the benzene group. IAA loses its ability to stimulate cell growth once the carboxyl group is detached, thus becoming a part of the inactive auxin pool.…”

Section: Introductionmentioning

confidence: 99%

Structural forms of hormone auxins in Madeira vines

et al. 2023

J Chinese Chemical Soc

X-ray diffraction and small-angle neutron scattering were used to identify the naturally occurring hormone auxin in Madeira vine. Two kinds of auxins belonging to indole-3-acetic acid (IAA, C 10 H 9 NO 2 ) and 4-chloroindole-3-acetic acid (4-Cl-IAA, C 10 H 8 ClNO 2 ) have been found. The appearance of well-defined x-ray diffraction peaks from the IAA as well as from the 4-Cl-IAA structures shows that the IAA and 4-Cl-IAA molecules that are produced at the shoot apex crystallize into periodic arrangements, rather than stay in molecular forms, upon transport downward through in stem. Small angle neutron scattering spectra reveal a progressive increase in the length of crystallized IAA and 4-Cl-IAA on transported downward from the shoot apex to the stem, reaching 59 nm in length in the area 8-9 cm below the shoot apex. A portion of IAA loses their carboxyl group COOH becoming inactive in stimulating cell growth, which slows down the growth in an aged stem.