Hormonal Signaling during dPCD: Cytokinin as the Determinant of RNase-Based Self-Incompatibility in Solanaceae

Biomolecules. 2023 Jun 23;13(7):1033. doi: 10.3390/biom13071033.

Abstract

Research into molecular mechanisms of self-incompatibility (SI) in plants can be observed in representatives of various families, including Solanaceae. Earlier studies of the mechanisms of S-RNase-based SI in petunia (Petunia hybrida E. Vilm.) demonstrate that programmed cell death (PCD) is an SI factor. These studies suggest that the phytohormon cytokinin (CK) is putative activator of caspase-like proteases (CLPs). In this work, data confirming this hypothesis were obtained in two model objects-petunia and tomato (six Solanaceae representatives). The exogenous zeatin treatment of tomato and petunia stigmas before a compatible pollination activates CLPs in the pollen tubes in vivo, as shown via the intravital imaging of CLP activities. CK at any concentration slows down the germination and growth of petunia and tomato male gametophytes both in vitro and in vivo; shifts the pH of the cytoplasm (PHc) to the acid region, thereby creating the optimal conditions for CLP to function and inhibiting the F-actin formation and/or destructing the cytoskeleton in pollen tubes to point foci during SI-induced PCD; and accumulates in style tissues during SI response. The activity of the ISOPENTENYLTRANSFERASE 5 (IPT5) gene at this moment exceeds its activity in a cross-compatible pollination, and the levels of expression of the CKX1 and CKX2 genes (CK OXIDASE/DEHYDROGENASE) are significantly lower in self-incompatible pollination. All this suggests that CK plays a decisive role in the mechanism underlying SI-induced PCD.

Keywords: RNase-based SI-induced PCD; actin cytoskeleton; caspase-like protease; cytokinin; pollen tube growth in vivo and in vitro.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cytokinins / metabolism
  • Endoribonucleases / metabolism
  • Humans
  • Peptide Hydrolases / metabolism
  • Petunia* / genetics
  • Petunia* / metabolism
  • Plant Proteins / genetics
  • Plant Proteins / metabolism
  • Pollen / metabolism
  • Ribonucleases / genetics
  • Solanaceae* / metabolism
  • Vegetables

Substances

  • Ribonucleases
  • Cytokinins
  • Plant Proteins
  • Endoribonucleases
  • Peptide Hydrolases

Grants and funding

This research was funded by the Ministry of Education and Science of Russian Federation (goszadanie No. FGUM-2022-0003).