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ARS Home » Midwest Area » Urbana, Illinois » Global Change and Photosynthesis Research » Research » Publications at this Location » Publication #353419

Title: The brassinosteroid receptor kinase, BRI1, plays a role in seed germination and the release of dormancy by cold stratification

item Kim, Sang Yeol
item WARPEHA, KATHERINE - University Of Illinois
item Huber, Steven

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/2/2019
Publication Date: 8/30/2019
Citation: Kim, S., Warpeha, K.M., Huber, S.C. 2019. The brassinosteroid receptor kinase, BRI1, plays a role in seed germination and the release of dormancy by cold stratification. Journal of Plant Physiology. 241. Article 153031.

Interpretive Summary: Seed dormancy and germination are critical developmental transitions that must be finely tuned by internal and external signals to avoid germination when conditions would be undesirable for seedling growth. Because optimal seed dormancy is critical for agricultural systems, it is imperative to understand all of the underlying mechanisms with a future goal of application for seed maintenance and crop yield. Internal signals controlling the release of seed dormancy are the plant hormones, gibberellins (GAs) and abscisic acid (ABA), and an important external signal is cold stratification (treatment of imbibed seeds for several days at low but non-freezing temperatures). Results obtained in the present study indicate that brassinosteroid (BR) signaling is required for cold stratification to break seed dormancy. Moreover, BRI1 appears to function upstream of GA and ABA signaling. These results add to our understanding of the role of BR signaling in the seed germination process.

Technical Abstract: Seed dormancy is a critical mechanism that delays germination until environmental conditions are favorable for growth. Plant hormones gibberellin (GA) and abscisic acid (ABA) have long been recognized as key players in regulating dormancy and germination. Recent data have increased interest in brassinosteroid (BR) hormones that promote germination by activating GA downstream genes and inactivating ABA signaling. Exposure of imbibed seeds to low temperature (cold stratification) is widely used to release seed dormancy and to improve germination frequency. However, the mechanism by which cold stratification overcomes the inhibitory role of ABA is not completely understood. In the present study, we show delayed germination of seeds of the BR in-sensitive mutant, bri1-5, that was largely reversed by treatment with fluridone, an inhibitor of ABA biosynthesis. In addition, the bri1-5 seeds were markedly less sensitive to the cold stratification release of dormancy. These results suggest that BR locates upstream of ABA signaling and downstream of cold stratification signaling in dormancy and germination pathways. Consistent with this notion, BR biosynthetic genes, DWF4 and DET2, were upregulated by cold stratification. The transcripts of the GA biosynthesis gene, GA3ox1, and cold responsive genes, CBF1 and CBF2, increased in response to cold stratification in wild type seeds but not in bri1-5 seeds. Conversely, transgenic seeds overexpressing BRI1 germinated more rapidly than wild type in the absence of cold stratification. Thus, we propose that BR signaling plays a previously unrecognized role in the cold stratification pathway for seed dormancy and germination.