Origin and Development of the Root Cap in Rice

Abstract

(J.X.).The tip of the root is covered by a thimble-shaped root cap that is the site of perception and transduction for many environmental stimuli. Until now, little was known about how the root cap of rice (Oryza sativa) develops and functions to regulate the adaptive behavior of the root. To address this, we examined the formation of the rice root cap during embryogenesis and characterized the anatomy and structure of the rice radicle root cap. We further investigated the role of the quiescent center in the de novo origin of the root cap. At the molecular level, we found that shoot-derived auxin was absolutely needed to trigger root cap regeneration when the quiescent center was removed. Our time-course analysis of transcriptomic dynamics during the early phases of root cap regeneration indicated that changes in auxin signaling and appropriate levels of cytokinin are critical for root cap regeneration after the removal of the root cap. Moreover, we identified 152 genes that produce root cap-specific transcripts in the rice root tip. These findings together offer, to our knowledge, new mechanistic insights into the cellular and molecular events inherent in the formation and development of the root cap in rice and provide a basis for future research on the developmental and physiological function of the root cap of monocot crops.

Analyses of Ca2+ dynamics using a ubiquitin‐10 promoter‐driven Yellow Cameleon 3.6 indicator reveal reliable transgene expression and differences in cytoplasmic Ca2+ responses in Arabidopsis and rice (Oryza sativa) roots

“…These experiments reveal that Glu also triggers a Ca 2+ response in the monocotyledonous plant rice and point to the conservation of an amino acid responsive Ca 2+ signaling system in this species. This is in agreement with the presence of a complex family of GLRs in rice and with their reported function (Li et al ., ; Wang et al ., ). However, considering both experiments, the hyperpolarization and Glu response analyses, our study also reveals fundamental differences in Ca 2+ signaling between the model species Arabidopsis and rice.…”

“…Moreover, recent studies revealed, for example, the conservation of complete Ca 2+ -activated modules for the regulation of potassium (K + ) uptake between Arabidopsis and rice (Xu et al, 2006;Li et al, 2014). Also, channels that are involved in the formation of Ca 2+ signals such as glutamate (Glu) receptor-like (GLR) proteins have been reported to fulfill crucial functions during rice development and environmental responses Wang et al, 2014). By contrast, despite several early reports about the role of Ca 2+ and calmodulin in rice stress responses, which were largely based on the application of inhibitors or agonists for Ca 2+ signaling, no high-resolution data on Ca 2+ signatures in rice have been reported to date (Aurisano et al, 1995;Yemelyanov et al, 2011).…”

Stem cell lineage in body layer specialization and vascular patterning of rice root and leaf

“…1b) [9,30], while the lateral root cap initial cell and the epidermal initial cell were separate in rice (Fig. 1a) [29]. Therefore, the lateral root cap in Arabidopsis seems to be a derivative of L1 structure.…”

“…1a). The rice root cap, which was initiated from the columella initial cell and lateral root cap initial cell [29], was independent from the three layers ( Fig. 1a).…”

Focus on Roots

“…Kumpf et al (2014) investigated how coordination of cell division between daughters of root meristem initials and their shift into endo-reduplication and elongation is important for correct root meristem function. Wang et al (2014) studied the establishment and regeneration of the rice root cap.…”