LATERAL ORGAN BOUNDARIES DOMAIN (LBD)10 interacts with SIDECAR POLLEN/LBD27 to control pollen development in Arabidopsis

Abstract

SUMMARYDuring male gametophyte development in Arabidopsis thaliana, the microspores undergo an asymmetric division to produce a vegetative cell and a generative cell, which undergoes a second division to give rise to two sperm cells. SIDECAR POLLEN/LATERAL ORGAN BOUNDARIES DOMAIN (LBD) 27 plays a key role in the asymmetric division of microspores. Here we provide molecular genetic evidence that a combinatorial role of LBD10 with LBD27 is crucial for male gametophyte development in Arabidopsis. Expression analysis, genetic transmission and pollen viability assays, and pollen development analysis demonstrated that LBD10 plays a role in the male gametophyte function primarily at germ cell mitosis. In the mature pollen of lbd10 and lbd10 expressing a dominant negative version of LBD10, LBD10:SRDX, aberrant microspores such as bicellular and smaller tricellular pollen appeared at a ratio of 10-15% with a correspondingly decreased ratio of normal tricellular pollen, whereas in lbd27 mutants, 70% of the pollen was aborted. All pollen in the lbd10 lbd27 double mutants was aborted and severely shrivelled compared with that of the single mutants, indicating that LBD10 and LBD27 are essential for pollen development. Gene expression and subcellular localization analyses of LBD10:GFP and LBD27:RFP during pollen development indicated that posttranscriptional and/or posttranslational controls are involved in differential accumulation and subcellular localization of LBD10 and LBD27 during pollen development, which may contribute in part to combinatorial and distinct roles of LBD10 with LBD27 in microspore development. In addition, we showed that LBD10 and LBD27 interact to form a heterodimer for nuclear localization.

The evolution and patterning of male gametophyte development

“…SCP is a microspore-specific LATERAL ORGAN BOUNDARIES-DOMAIN/ASYMMETRIC LEAVES2-LIKE (LBD/ASL) domain family protein, whose expression overlaps with that of other family members in developing pollen. SCP (LBD27) and LBD10 form nuclear-localised heterodimers and act synergistically to control pollen development (Kim et al, 2015). Thus, combinatorial interactions among LBD proteins are thought to be important for their roles in the male gametophyte (Kim et al, 2016).…”

Combinatorial interactions between LBD10 and LBD27 are essential for male gametophyte development in Arabidopsis

“…15 Analysis of mature pollen grains and developmental analysis indicated that LBD10 is involved in microspore polarization prior to the first asymmetric division and also in germ cell mitosis. These results indicated that LBD10 plays an overlapping role with LBD27 during PMI, but also plays a distinct role during PMII.…”

Structural analysis reveals a “molecular calipers” mechanism for a LATERAL ORGAN BOUNDARIES DOMAIN transcription factor protein from wheat

“…Recent studies have expanded their functional diversity beyond the definition of lateral organ boundaries. The LBD family proteins also play pivotal roles in pollen development (9,10), vascular differentiation (11), nitrogen metabolism (12), plant regeneration (13,14), photomorphogenesis (15), disease susceptibility (16,17), and some specific developmental processes in wood and grass species (18,19).…”

“…Homo-and heterodimerization are generally observed within LBD proteins (10,50). However, it was not clear whether LBD proteins function as monomers in cells.…”