The role of snoRNP in thermospermine-mediated Arabidopsis thaliana growth and development was found to be found in the study

Polyamines are widely found in
bacteria, yeast, animals and plants.
The main forms of polyamines are Putrescine (Put), spermidine (Spd) and spermine (Spm).

Polyamines have been considered to be potential plant hormones that regulate multiple aspects of plant growth and development and environmental adaptation, but because the endogenous content is much higher than that of classical plant hormones and the signal transduction pathway is not clear, it has been considered to function
only as a growth regulator in recent years.
In 1979, Thermospermine (T-Spm) was identified in Thermus thermophilus as an isomer
of spermine.
The phenotypes of priospermine synthesis defective mutants in Arabidopsis thaliana differed significantly from those of putrescine, spermidine and spermine-deficient mutants, indicating that glycamine may have specific functions and signal transduction pathways
in plants.

The research group of Li Jiayang, a researcher at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences, measured the content of polyamines in Arabidopsis thaliana and found that the endogenous content of hot spermine was significantly lower than that of putrescine, spermidine and spermine, reaching the range of
classical plant hormones.
The plant height of ACL5, a thermospermine synthesis mutant, was significantly reduced, and a tumor-like structure
appeared in the root near the rhizome junction.
In order to analyze the mechanism of thermospermine regulating plant growth and development, the scientific research team carried out large-scale inhibitor screening and obtained more than 50 suppressors of acl5 nodule structure (san).

。 In-depth research on two of the inhibitors, san1 and san2, found that SAN1 and SAN2 encode NAP57 and NOP56, the core proteins of the box H/ACA and box C/D snoRNP complexes, respectively, and have point mutations
in the conserved TruB N and Nop domains, respectively 。 Previous studies in bacteria, yeast and animals have shown that box H/ACA and box C/D snoRNP complexes are composed of four core proteins and corresponding small molecule nucleolar RNA (snoRNA), respectively, responsible for pseudouracilation modification and 2'-O-methylation modification of ribosomal RNA (rRNA), which are closely related
to the biosynthesis and activity of ribosomes and the occurrence of diseases such as cancer 。 The core proteins of box H/ACA and C/D snoRNP complexes in plants are highly homologous to the core proteins in yeast and animals, but the functional study of snoRNP complexes in plants is limited
.

Through mass spectrometry quantification of rRNA pseudouracilation modification, it was found that there was no significant difference between the level of pseudouracilation modification in acl5 and the wild type, while the level of pseudouracilation modification in acl5 san1 was significantly reduced, indicating that the point mutation in SAN1 caused damage
to box H/ACA snoRNP function 。 The researchers used high-throughput sequencing technology to detect the 2'-O-methylation modification site and degree in 5.
8S, 18S and 25S rRNA, and found that the 2'-O-methylation modification level of acl5 was not significantly different from that of wild type, while the level of 2'-O-methylation modification of rRNA in acl5 san2 decreased globally, indicating that SAN2 plays an important role
in rRNA 2'-O-methylation modification.

In Arabidopsis, putrescine, spermidine, spermidine, and thermospermine are the main types of polyamines, and their endogenous content and biological function are different
.
The study found endogenous levels of thermospermine to be about 1 μg/g, close to the range of
endogenous plant hormones.
The inhibitor proteins SAN1/NAP57 and SAN2/NOP56 of acl5 were identified through genetic screening, which are core components in box H/ACA snoRNP and box C/D snoRNP, respectively, and play a key role
in the pseudouracilation modification and 2'-O-methylation modification of rRNA.
Therefore, the in-depth analysis of snoRNP function is expected to elucidate the signal transduction mechanism
of snospermine in plants by regulating the function of snoRNP complexes.

This study links rRNA modification with thermospermine-mediated plant growth and development, which provides important evidence
for studying the mechanism of thermospermine regulating plant growth and development.
Due to the low endogenous content of glycamine, it may function as a new class of plant hormones, and more analysis of ACL5 inhibitors and in-depth study of snoRNP function are needed in the future, which is of great significance
for revealing the complete signal transduction pathway of thermospermine in plants.

The research results, titled SnoRNP is essential for thermospermine-mediated development in Arabidopsis thaliana, were published in SCIENCE CHINA Life Sciences
。 The research work is supported
by the National Natural Science Foundation of China, the Strategic Leading Science and Technology Project of the Chinese Academy of Sciences, the National Key Research and Development Program, the Youth Innovation Promotion Association of the Chinese Academy of Sciences and the Key Technical Talents Program of the Chinese Academy of Sciences.

A working model of T-SPM regulating Arabidopsis thaliana growth and development