J Integr Plant Biol. ›› 2022, Vol. 64 ›› Issue (3): 702-716.DOI: 10.1111/jipb.13197

• Plant Reproduction Biology • Previous Articles     Next Articles

Interaction of brassinosteroid and cytokinin promotes ovule initiation and increases seed number per silique in Arabidopsis

Song‐Hao Zu1,2†, Yu‐Tong Jiang1†, Jin‐Hui Chang1, Yan‐Jie Zhang1, Hong‐Wei Xue2 and Wen‐Hui Lin1,2*   

  1. 1 School of Life Sciences and Biotechnology, The Joint International Research Laboratory of Metabolic and Developmental Sciences, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China
    2 School of Agriculture and Biology, Joint Center for Single Cell Biology, Shanghai Jiao Tong University, Shanghai 200240, China

    These authors contributed equally to this work.
    Correspondence: Wen‐Hui Lin (whlin@sjtu.edu.cn)
  • Received:2021-10-13 Accepted:2021-11-25 Online:2021-11-27 Published:2022-03-01

Abstract:

Ovule initiation is a key step that strongly influences ovule number and seed yield. Notably, mutants with enhanced brassinosteroid (BR) and cytokinin (CK) signaling produce more ovules and have a higher seed number per silique (SNS) than wild-type plants. Here, we crossed BR- and CK-related mutants to test whether these phytohormones function together in ovule initiation. We determined that simultaneously enhancing BR and CK contents led to higher ovule and seed numbers than enhancing BR or CK separately, and BR and CK enhanced each other. Further, the BR-response transcription factor BZR1 directly interacted with the CK-response transcription factor ARABIDOPSIS RESPONSE REGULATOR1 (ARR1). Treatments with BR or BR plus CK strengthened this interaction and subsequent ARR1 targeting and induction of downstream genes to promote ovule initiation. Enhanced CK signaling partially rescued the reduced SNS phenotype of BR-deficient/insensitive mutants whereas enhanced BR signaling failed to rescue the low SNS of CK-deficient mutants, suggesting that BR regulates ovule initiation and SNS through CK-mediated and -independent pathways. Our study thus reveals that interaction between BR and CK promotes ovule initiation and increases seed number, providing important clues for increasing the seed yield of dicot crops.

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