Expression of auxin transporter genes in flax (Linum usitatissimum) fibers during gravity response

Gravitropism is an adaptive reaction of plants associated with the ability of various plant organs to be located and to grow in a certain direction relative to the gravity vector, while usually the asymmetric distribution of the phytohormone auxin is a necessary condition for the gravitropical bending of plant organs. Earlier, we described significant morphological changes in phloem fibers with a thickened cell wall located on different sides of the stem in the area of the gravitropic curvature. The present study is the first work devoted to the identification of genes encoding auxin transporters in cells at different stages of development and during gravity response. In this study, the flax genes encoding the AUX1/LAX, PIN-FORMED, PIN-LIKES, and ABCB auxin transporters were identified. A comparative analysis of the expression of these genes in flax phloem fibers at different stages of development revealed increased expression of some of these genes at the stage of intrusive growth (LusLAX2 (A, B), LuxPIN1-D, LusPILS7 (C, D)), at the early stage of tertiary cell wall formation (LusAUX1 (A, D), LusABCB1 (A, B), LusABCB15-A, LusPIN1 (A, B), LusPIN4-A, and LusPIN5-A), and at the late stage of tertiary cell wall development (LusLAX3 (A, B)). It was shown that in the course of gravitropism, the expression of many genes, including those responsible for the influx of auxin in cells (LusAUX1-D), in the studied families increased. Differential expression of auxin transporter genes was revealed during gravity response in fibers located on different sides of the stem (upper (PUL) and lower (OPP)). The difference was observed due to the expression of genes, the products of which are responsible for auxin intracellular transport (LusPILS3, LusPILS7-A) and its efflux (LusABCB15-B, LusABCB19-B). It was noted that the increased expression of PIN genes and ABCB genes was more typical of fibers on the opposite side. The results obtained allow us to make an assumption about the presence of differential auxin content in the fibers of different sides of gravistimulated flax plants, which may be determined by an uneven outflow of auxin. This study gives an idea of auxin carriers in flax and lays the foundation for further studies of their functions in the development of phloem fiber and in gravity response.

1. Adamowski M., Friml J. PIN-dependent auxin transport: action, regulation, and evolution. Plant Cell. 2015;27(1):20-32. DOI 10.1105/tpc.114.134874

2. Bao Y., Huang X., Rehman M., Wang Y., Wang B., Peng D. Identification and expression analysis of the PIN and AUX/LAX gene families in ramie (Boehmeria nivea L. Gaud). Agronomy. 2019;9:435. DOI 10.3390/agronomy9080435

3. Barbez E., Kubeš M., Rolcík J., Béziat C., Pencík A., Wang B., Rosquete M.R., Zhu J., Dobrev P.I., Lee Y., Zažímalovà E., Petrášek J., Geisler M., Friml J., Kleine-Vehnet J. A novel putative auxin carrier family regulates intracellular auxin homeostasis in plants. Nature. 2012;485(7396):119-122. DOI 10.1038/nature11001

4. Cho M., Cho H.T. The function of ABCB transporters in auxin transport. Plant Signal. Behav. 2013;8(2):e22990. DOI 10.4161/psb.22990

5. Evans M.L. Gravitropism: interaction of sensitivity modulation and effector redistribution. Plant Physiol. 1991;95(1):1-5. DOI 10.1104/pp.95.1.1

6. Friml J., Wiśniewska J., Benkova E., Mendgen K., Palme K. Lateral relocation of auxin efflux regulator PIN3 mediates tropism in Arabidopsis. Nature. 2002;415(6873):806-809. DOI 10.1038/415806a

7. Geisler M., Aryal B., Donato M., Hao P.A. Critical view on ABC transporters and their interacting partners in auxin transport. Plant Cell Physiol. 2017;58(10):1601-1614. DOI 10.1093/pcp/pcx104

8. Gerttula S., Zinkgraf M., Muday G., Lewis D., Ibatullin F., Brumer H., Hart F., Mansfield S., Filkov V., Groovera A. Transcriptional and hormonal regulation of gravitropism of woody stems in Populus. Plant Cell. 2015;27(10):2800-2813. DOI 10.1105/tpc.15.00531

9. Gorshkova T.A., Sal’nikov V.V., Chemikosova S.B., Ageeva M.V., Pavlencheva N.V. The snap point: a transition point in Linum usitatissimum bast fiber development. Ind. Crops Prod. 2003;18(3):213-221. DOI 10.1016/S0926-6690(03)00043-8

10. Harrison M.A., Pickard B.G. Auxin asymmetry during gravitropism by tomato hypocotyls. Plant Physiol. 1989;89(2):652-657. DOI 10.1104/pp.89.2.652

11. Haygreen J.G., Bowyer J.L. Forest Products and Wood Science. Wiley-Blackwell, 1996

12. Hellgren J.M., Olofsson K., Sundberg B. Patterns of auxin distribution during gravitational induction of reaction wood in poplar and pine. Plant Physiol. 2004;135(1):212-220. DOI 10.1104/pp.104.038927

13. Ibragimova N.N., Ageeva M.V., Gorshkova T.A. Development of gravitropic response: unusual behavior of flax phloem G-fibers. Protoplasma. 2017;254(2):749-762. DOI 10.1007/s00709-016-0985-8

14. Ibragimova N., Mokshina N., Ageeva M., Gurjanov O., Mikshina P. Rearrangement of the cellulose-enriched cell wall in flax phloem fibers over the course of the gravitropic reaction. Int. J. Mol. Sci. 2020;21(15):5322. DOI 10.3390/ijms21155322

15. Jenness M.K., Tayengwa R., Bate G.A., Tapken W., Zhang Y., Pang C., Murphy A.S. Loss of multiple ABCB auxin transporters recapitulates the major twisted dwarf 1 phenotypes in Arabidopsis thaliana. Front. Plant Sci. 2022;13:840260. DOI 10.3389/fpls.2022.840260

16. Jourez B., Riboux A., Leclercq A. Anatomical characteristics of tension wood and opposite wood in young inclined stems of poplar (Populus euramericana cv ʻGhoyʼ). IAWA J. 2001;22(2):133-157. DOI 10.1163/22941932-90000274

17. Kaneda M., Schuetz M., Lin B.S., Chanis C., Hamberger B., Western T.L., Ehlting J., Samuelset A.L. ABC transporters coordinately expressed during lignifications of Arabidopsis stems include a set of ABCBs associated with auxin transport. J. Exp. Bot. 2011;62(6): 2063-2077. DOI 10.1093/jxb/erq416

18. Kang J., Park J., Choi H., Burla B., Kretzschmar T., Lee Y., Martinoia E. Plant ABC transporters. Arabidopsis Book. 2011;9:e0153. DOI 10.1199/tab.0153

19. Li Y., Hagen G., Guilfoyle T.J. An auxin-responsive promoter is differentially induces by auxin gradients during tropisms. Plant Cell. 1991;3(11):1167-1175. DOI 10.1105/tpc.3.11.1167

20. Manna M., Rengasamy B., Ambasht N.K., Sinha A.K. Characterization and expression profiling of PIN auxin efflux transporters reveal their role in developmental and abiotic stress conditions in rice. Front. Plant Sci. 2022;13:1059559. DOI 10.3389/fpls.2022.1059559

21. Mokshina N., Gorshkov O., Takasaki H., Onodera H., Sakamoto S., Gorshkova T., Mitsuda N. FIBexDB: a new online transcriptome platform to analyze development of plant cellulosic fibers. New Phytol. 2021;231(2):512-515. DOI 10.1111/nph.17405

22. Rakusová H., Han H., Valošek P., Friml J. Genetic screen for factors mediating PIN polarization in gravistimulated Arabidopsis thaliana hypocotyls. Plant J. 2019;98(6):1048-1059. DOI 10.1111/tpj.14301

23. Swarup R., Péret B. AUX/LAX family of auxin influx carriers – an over-view. Front. Plant Sci. 2012;3:225. DOI 10.3389/fpls.2012.00225

24. Timell T.E. The chemical composition of tension wood. Svensk Papperstidning. 1969;72:173-181

25. Young G.B., Jack D.L., Smith D.W., Saier M.H., Jr. The amino acid/ auxin:proton symport permease family. Biochim. Biophys. Acta. 1999;1415(2):306-322. DOI 10.1016/s0005-2736(98)00196-5

26. Zažímalová E., Murphy A.S., Yang H., Hoyerová K., Hošek P. Auxin transporters – why so many? Cold Spring Harb. Perspect. Biol. 2010;2(3):a001552. DOI 10.1101/cshperspect.a001552

27. Zhang Y., Hartinger C., Wang X., Friml J. Directional auxin fluxes in plants by intramolecular domain-domain coevolution of PIN auxin transporters. New Phytol. 2020;227(5):1406-1416. DOI 10.1111/nph.16629

28. Zhu Q., Gallemı́ M., Pospı́šil J., Žádnı́ková P., Strnad M., Benková E. Root gravity response module guides differential growth determining both root bending and apical hook formation in Arabidopsis. Development. 2019;146(17):dev175919. DOI 10.1242/dev.175919.