Page 145 - PC2019 Program & Proceedings

PLANT CANADA 2019

S75. Can phloem derived small RNA modify gene regulation in shoot stem cells?
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Minow, M. ; V. Coneva; V. Lesy; M. Misyura; J. Colasanti
University of Guelph

Plant small RNA (sRNA) can regulate genes by post transcriptional gene silencing (PTGS) through
repressing mRNA, or transcriptional gene silencing (TGS) through RNA-directed DNA methylation
(RdDM). The phloem contains sRNA; however, it is unknown if phloem derived sRNA can reach the
shoot apical meristem (SAM). To test phloem-to-SAM sRNA transport, transgenic Arabidopsis plants
were created with a phloem specific promoter driving an RNA interference cassette targeting the floral
regulator FLOWERINGLOCUS D (FD), which is constitutively expressed in the SAM. These transgenic
plants showed significantly delayed flowering through reduced FD transcript levels. Late flowering
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caused by the FD interference transgene was not observed in sRNA biogenesis mutants or fd mutants. A
parallel synthetic biology approach was devised to test whether phloem sRNA can move to the stem cell
subdomain within the SAM, which is defined by CLAVATA3 (CLV3) gene expression. A clv3-2 deletion
mutant was transformed with a CLV3 transgene modified to include a synthetic sRNA target site and
driven by its native promoter. These rescued plants were then transformed with an artificial microRNA
(aMIR) targeting the synthetic CLV3 site and driven by a phloem-specific promoter. Several independent
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aMIR lines showed strong clv defects. These findings demonstrate that phloem-to-SAM sRNA
trafficking occurs, which has implications for long distance signals altering stem cell activity. Potential
epigenetic alterations that give rise to transgenerational effects will be discussed.

Mark Minow (mminow@uoguelph.ca)

S76. Characterization of B-genome specific high copy hAT MITE families in Brassica genome
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Perumal, S. ; I. Parkin
1 Agriculture and Agri-Food Canada (AAFC)

Miniature inverted-repeat transposable elements (MITEs) are non-autonomous class II transposon which
has shown to influence the evolution of genomes. Brassica nigra (B-genome) is one of the three widely
cultivated Brassica diploids primarily as an oil crop, which harbors important traits for Breeding value.
However, limited genetic knowledge about the B-genome has hindered utilizing these agronomically
important traits. Here, we characterized two new high copy hAT MITE families (BnHAT-1 and BnHAT-
2) in the B-genome and comparatively analyzed with its related diploids, B. rapa (A) and B. oleracea (C).
Both MITE families were present as high copy elements in B-genome as 420 and 329 copies of BnHAT-1
and BnHAT-2, respectively, while less than 20 elements were identified in A, and C -genomes,
supporting the B-genome specific proliferation of both MITE families. In addition, 44% and 47% of the
B-genome members were present in ≤ 2 kb flanking region in the vicinity of the genome speculating the
MITEs influence to the gene structure and function. Insertion time analysis of MITEs has revealed that
the major proliferation MITEs occurred ≤ 2 million years ago. Site-specific polymorphism analyses
showed that 44% MITEs were actively amplified into the B-genome. Overall this study elucidates a
comprehensive understanding of two B-genome specific high copy MITE families, and also role on the B-
genome evolution also discussed.

Sampath Perumal (bioteksampath@gmail.com)

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