New Insights Into the Local Auxin Biosynthesis and Its Effects on the Rapid Growth of Moso Bamboo (Phyllostachys edulis)

Abstract

Auxin plays a crucial regulatory role in higher plants, but systematic studies on the location of auxin local biosynthesis are rare in bamboo and other graminaceous plants. We studied moso bamboo (Phyllostachys edulis), which can grow up to 1 m/day and serves as a reference species for bamboo and other fast-growing species. We selected young tissues such as root tips, shoot tips, young culm sheaths, sheath blades, and internode divisions for local auxin biosynthesis site analysis. IAA immunofluorescence localization revealed that auxin was similarly distributed in different stages of 50-cm and 300-cm bamboo shoots. Shoot tips had the highest auxin content, and it may be the main site of auxin biosynthesis in the early stage of rapid growth. A total of 22 key genes in the YUCCA family for auxin biosynthesis were identified by genome-wide identification, and these had obvious tissue-specific and spatio-temporal expression patterns. In situ hybridization analysis revealed that the localization of YUCCA genes was highly consistent with the distribution of auxin. Six major auxin synthesis genes, PheYUC3-1, PheYUC6-1, PheYUC6-3, PheYUC9-1, PheYUC9-2, and PheYUC7-3, were obtained that may have regulatory roles in auxin accumulation during moso bamboo growth. Culm sheaths were found to serve as the main local sites of auxin biosynthesis and the auxin required for internode elongation may be achieved mainly by auxin transport.

Deciphering the Molecular Mechanism of the Intermediate Secondary Growth and Internode Elongation of the Castor Bean (Ricinus communis L.) by the Combined Analysis of the Transcriptome and Metabolome

“…These findings suggest that the inhibition of stem growth controlled by phytochrome can be attributed to a decrease in free IAA levels [27]. Similar findings were obtained for Trifoliate Orange (Poncirus trifoliata L.), Moso Bamboo (Phyllostachys edulis), and rice, where IAA was identified as the key hormone positively regulating plant internode elongation [28][29][30].…”

Effect of Low Light Stress on Distribution of Auxin (Indole-3-Acetic Acid) between Shoot and Roots and Development of Lateral Roots in Barley Plants

“…In the present experiments, the decrease in IAA concentration in the shoots, roots and phloem found in barley plants under low illumination can be explained by inhibition of auxin synthesis in the shoots and its transport to the roots. Although root tips of Arabidopsis thaliana can synthesize auxin, the main sites of auxin synthesis are located in the young leaves and the tips of stems [ 21 ]. Therefore, changes in the production of IAA in leaves and its delivery to roots are the most likely candidates for the role of a long-distance signal sent from shoots to roots.…”

Photosynthesis, Phytohormone Signaling and Sugar Catabolism in the Culm Sheaths of Phyllostachys edulis

“…The rapid growth of bamboo is mainly due to the vigorous division and rapid elongation of internode cells, and plant hormones play a very important role in plant growth and development. Our group has reported for the first time that the culm sheath is the main site of auxin synthesis, transporting synthesized auxin to the connected internodes and thus regulating internode elongation [ 36 ]. Endogenous brassinosteroids (BRs) are the main factors promoting internode elongation in bamboo shoots [ 37 ].…”