The Legume SHR-SCR Module Predetermines Nodule Founder Cell Identity

doi:10.11983/CBB20182

Abstract

Abstract: Symbiotic nitrogen fixation between legumes and rhizobia is the most important nitrogen source for sustainable agriculture. As the final accommodation for rhizobia, the specialized lateral organ, root nodule, that provides the essential microenvironments for rhizobia and its proper development, is vital for biological nitrogen fixation. Nodule de novo organogenesis mainly initiates from cortical cell division and it is generally accepted that cortical cells of legumes possess certain identity, which enables them to respond to and establish symbiosis with rhizobia, but the underlying mechanisms remain unknown. Recently a team led by Ertao Wang in Centre for Excellence in Molecular Plant Science, Chinese Academy of Science showed that the SHORTROOT-SCARECROW (SHR-SCR) module predetermines this cortical cell identity in legumes. This study uncovers a novel molecular mechanism for nodule organogenesis, and provides important clues for an evolutionary understanding of root nodule symbiosis, which is both practically and theoretically valuable for improving nitrogen fixation efficiency in legumes and engineering nitrogen symbiosis in non-legumes.

Key words: legume-rhizobial nitrogen fixing symbiosis, biological nitrogen fixation, Medicago truncatula, nodule organo-genesis, SHR-SCR, cortical cell division

Chengwu Liu, Zhong Zhao. The Legume SHR-SCR Module Predetermines Nodule Founder Cell Identity[J]. Chinese Bulletin of Botany, 2020, 55(6): 661-665.

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URL: https://www.chinbullbotany.com/EN/10.11983/CBB20182

https://www.chinbullbotany.com/EN/Y2020/V55/I6/661

Figures/Tables 1

Figure 1 The legume SHR-SCR module predetermines cortical cell identity for cell division and accommodation of rhizobia (A) Longitudinal section of a developing Medicago truncatula nodule illustrating coordinated nodule organogenesis and rhizobial infection, which are the two fundamental processes during legume-rhizobial nitrogen fixing symbiosis (Bracket indicates that the majority of nodule cells originates from cortical cell division, and only these cells and the epidermal cells can be infected by rhizobia, arrow indicates root hair, arrowheads indicate rhizobial infection threads (magenta color)); (B) Differential SCR gene expression and SHR protein accumulation between Arabidopsis thaliana (left) and M. truncatula (right). Ep: Epidermis; Co: Cortex; En: Endodermis; Pe: Pericycle. The red indicates SHR expression in pericycle; green indicates SCR expressions in the endodermis of A. thaliana root, and the endodermis, cortex and epidermis in M. truncatula; yellow indicates SHR protein accumulation in the endodermis of A. thaliana, and the endodermis, cortex and epidermis in M. truncatula.

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