Distinct Hormone Signalling-Modulation Activities Characterize Two Maize Endosperm-Specific Type-A Response Regulators

Abstract

ZmTCRR1 and 2 are type-A response regulators expressed in the maize endosperm transfer cells (TC). While type-B response regulators transcriptionally control canonical type-A response regulators, as part of the cytokinin signal transduction mechanism, the ZmTCRRs are regulated by ZmMRP1, a master regulator of TC identity. In addition, the corresponding proteins are not detected in the TC, accumulating in the inner endosperm cells instead. These features suggest these molecules are not involved in classical, cell-autonomous, cytokinin signalling pathways. Using transgenic Arabidopsis plants ectopically expressing these genes, we have shown that ZmTCRR1 and 2 can modulate auxin and cytokinin signalling, respectively. In Arabidopsis, the ectopic expression of ZmTCRR2 blocked, almost completely, cytokinin perception. Given the conservation of these signalling pathways at the molecular level, our results suggest that the ZmTCRRs modulate cytokinin and auxin perception in the inner endosperm cells.

Toward unveiling transcriptome dynamics and regulatory modules at the maternal/filial interface of developing maize kernel

“…BETL1 , BETL2 , BETL3 , BETL4 , BETL9 , BETL9‐like , and BETL10 might have functions related to plant defense (Royo et al., 2014; Serna et al., 2001; Wei & Zhong, 2014). Recent studies suggest that ZmTCRR1 and ZmTCRR2 modulate auxin and cytokinin signaling during endosperm cell development (Royo et al., 2022). The maternally expressed gene1 ( ZmMEG1 ), which is exclusively expressed in BETL and inherited from the maternal parent, is important in BETL differentiation and nutrient uptake (Gutierrez‐Marcos et al., 2004).…”