Rice microtubule‐associated protein IQ67‐DOMAIN14 regulates grain shape by modulating microtubule cytoskeleton dynamics

Abstract

Summary Cortical microtubule (MT) arrays play a critical role in plant cell shape determination by defining the direction of cell expansion. As plants continuously adapt to ever‐changing environmental conditions, multiple environmental and developmental inputs need to be translated into changes of the MT cytoskeleton. Here, we identify and functionally characterize an auxin‐inducible and MT‐localized protein OsIQ67‐DOMAIN14 (OsIQD14), which is highly expressed in rice seed hull cells. We show that while deficiency of OsIQD14 results in short and wide seeds and increases overall yield, overexpression leads to narrow and long seeds, caused by changed MT alignment. We further show that OsIQD14‐mediated MT reordering is regulated by specifically affecting MT dynamics, and ectopic expression of OsIQD14 in Arabidopsis could change the cell shape both in pavement cells and in hypocotyl cells. Additionally, OsIQD14 activity is tightly controlled by calmodulin proteins, providing an alternative way to modify the OsIQD14 activity. Our results indicate that OsIQD14 acts as a key factor in regulating MT rearrangements in rice hull cells and hence the grain shape, and allows effective local cell shape manipulation to improve the rice yield trait.

New Insights Into Functions of IQ67-Domain Proteins

“…GW5 is an IQD protein located in the plasma membrane and is involved in brassinosteroid signaling. And It is similar to OsIQD14 about its regulation of seed shape ( Duan et al, 2017 ; Liu et al, 2017 ; Yang et al, 2020 ).…”

“…Rice is an important crop that has been subject to extensive efforts to increase grain size and yields. Rice OsIQD14 ( Yang et al, 2020 ), an IQD family protein, is highly expressed in rice seed hull cells, regulating microtubule cytoskeletal dynamics to control rice grain size. In addition to localizing to the nucleus and cytoplasm, OsIQD14 also distributes along microtubules.…”

“…OsIQD14 controls cytoskeletal dynamics and cell morphology in rice by integrating auxin and calcium signaling pathways to increase rice yield. Regarding its specific mechanism, many hypotheses have been proposed, including the interaction among OsIQD14, SPR2 and CaM proteins is regulated by auxin/blue light and Ca2 + signal ( Yang et al, 2020 ). Moreover, it is unclear whether there are other microtubule-related proteins such as katanin, MOR1, and Augmin involved with the process, and how they regulate microtubule dynamics and respond to environment signals.…”

A 24,482-bp Deletion Increases Seed Weight Through Multiple Pathways in Rapeseed (Brassica Napus L.)

“…Examining seed coat cells will therefore help us better understand seed formation. SEM has been effectively applied in Arabidopsis and many crops to reveal the morphology of cells at the surface of the seed coat (Huang et al 2017;Lyu et al 2020;Xu et al 2018;Yang et al 2019).…”

OsRRM, an RNA-Binding Protein, Modulates Sugar Transport in Rice (Oryza sativa L.)

“…Dry seeds were pretreated as described by Yang et al (2019) before scanning electron microscopy observation (S-3000N; Hitachi). Cell number counting was performed using ImageJ software.…”