20190916 Development

Abiotic stress modulates root patterning via ABA-regulated microRNA expression in the endodermis initials

Daria Bloch, Malikarjuna Rao Puli, Assaf Mosquna, Shaul Yalovsky

Development  2019  146: dev177097 doi: 10.1242/dev.177097  Published 2 September 2019

ABSTRACT

Patterning of the root xylem into protoxylem (PX) and metaxylem is regulated by auxin-cytokinin signaling and microRNA miR165a/166b-mediated suppression of genes encoding Class III HOMEODOMAIN LEU-ZIPPER (HD-ZIPIII) proteins. We found that, in Arabidopsis, osmotic stress via core abscisic acid (ABA) signaling in meristematic endodermal cells induces differentiation of PX in radial and longitudinal axes in association with increased VND7 expression. Similarly, in tomato, ABA enhanced PX differentiation longitudinally and radially, indicating an evolutionarily conserved mechanism. ABA increased expression of miR165a/166b and reduced expression of the miR165a/166b repressor ZWILLE (ZLL) (also known as ARGONAUTE10), resulting in reduced levels of all five HD-ZIPIII RNAs. ABA treatments failed to induce additional PX files in a miR165a/166b-resistant PHB mutant, phb1-d, and in scr and shr mutants, in which miR165a/166b expression is strongly reduced. Thus, ABA regulates xylem patterning and maturation via miR165a/166b-regulated expression of HD-ZIPIII mRNAs and associated VND7 levels. In lateral root initials, ABA induced an increase in miR165a levels in endodermal precursors and inhibited their reduction in the future quiescent center specifically at pre-emergence stage. Hence, ABA-induced inhibition of lateral root is associated with reduced HD-ZIPIII levels.

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非生物逆境會經由控制內皮層內離層酸調控的microRNA的表現來影響植物根的型態發育

摘要

植物根部篩管中，原生與繼生木質部組織的分佈是經由生長素-細胞分裂素下游訊息，以及由microRNA（miR165a/166b）來抑制第三類HD-ZIP蛋白質表現的機制所共同調節的。在阿拉伯芥中我們發現，由滲透壓不同所帶來的環境壓力會引起原生木質部細胞在輻射與垂直方向的分化，而此現象是經由離層酸在根部幹細胞區域的內皮層中，增加VND7轉錄因子表現所引起。同樣的，在番茄中也可以發現離層酸會增加原生維管束在輻射與垂直方向的分化，表示這個調控機制在演化壓力之下被保存了下來。離層酸會誘導miR165a/166b的表現，並且同時降低miR165a/166b的抑制蛋白ZWILLE（也稱作AGONAUTE10）的表現，進而減少了所有第三類HD-ZIP蛋白質的RNA總量。在miR165a/166b調控區域有變異的PHB轉殖植物中，和在已知miR165a/166b表現量大幅減低的突變植物中（phb1-d, scr 和 shr），處理離層酸並無法引起原生木質部的額外分化。因此，離層酸調控木質部的分佈與成熟是經由miR165a/166b來調控第三類HD-ZIP的表現量，最終影響了主要的轉錄因子VND7的表現。在側根發育起始時期，離層酸會增加miR165在內皮層的前驅細胞中的表現量，並且在側根生長的前期，miR165在靜默中心會特別被抑制。因此，由離層酸所引起的抑制側根生長與HD-ZIP表現量的降低有相當的關聯。

原文連結

https://dev.biologists.org/content/146/17/dev177097.abstract