Abstract
Despite the existence of considerable research on somatic embryogenesis (SE), the molecular mechanism that regulates the biosynthesis of auxins during the SE induction process remains unknown. Indole-3-acetic acid (IAA) is an auxin that is synthesized in plants through five pathways. The biosynthetic pathway most frequently used in this synthesis is the conversion of tryptophan to indol-3-pyruvic acid (IPA) by tryptophan aminotransferase of Arabidopsis (TAA) followed by the conversion of IPA to IAA by enzymes encoded by YUCCA (YUC) genes of the flavin monooxygenase family; however, it is unclear whether YUC-mediated IAA biosynthesis is involved in SE induction. In this study, we report that the increase of IAA observed during SE pre-treatment (plants in MS medium supplemented with 1-naphthaleneacetic acid (NAA) 0.54 µM and kinetin (Kin) 2.32 µM for 14 days) was due to its de novo biosynthesis. By qRT-PCR, we demonstrated that YUC gene expression was consistent with the free IAA signal found in the explants during the induction of SE. In addition, the use of yucasin to inhibit the activity of YUC enzymes reduced the signal of free IAA in the leaf explants and dramatically decreased the induction of SE. The exogenous addition of IAA restored the SE process in explants treated with yucasin. Our findings suggest that the biosynthesis and localization of IAA play an essential role during the induction process of SE in Coffea canephora.
Highlights
Plants, unlike animals, have a high capacity for regeneration of new individuals identical to the mother from a cell or groups of cells without the need for fertilization
We showed that CcYUC-mediated Indole-3-acetic acid (IAA) biosynthesis is required during the somatic embryogenesis (SE) induction process in C. canephora
These results revealed that the YUC-mediated biosynthesis of the auxin IAA is critical for SE in C. canephora
Summary
Unlike animals, have a high capacity for regeneration of new individuals identical to the mother from a cell or groups of cells without the need for fertilization. Our primary goal in this work was to determine whether YUC-mediated IAA biosynthesis is involved in the SE induction process in Coffea canephora. To answer this question, we used RT-qPCR to measure the transcription levels of CcYUC and used a specific yucasin inhibitor to block the biosynthesis of the auxin IAA. IInn oouurr ssttuuddyy,, oonn DDaayy 00,, wwee ffoouunndd aa ssttrroonngg ffrreeee IIAAAA ssiiggnnaall dduurriinngg tthhee SSEE iinndduuccttiioonn pprroocceessss ((FFiigguurree 66BB))..TThheesisginganladl edcerceraesaesdefdrofmrom d7aid(Faiig(uFriegu6Cre) t6hCr)outhgrho1u4gdha1i 4(Fdigaui r(eF6igDu)r.eA6t D21).dAait(F2i1gudraei (6FEi)g,uthree I6AEA), tshigenIaAlAbesgiagnnatol binecgraenasteo. AEnfefepchtoorfathe Inhibition of Auxin IAA Biosynthesis by Yucasin during the SE Induction Process in C. canephora.
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