Cold stress inhibits normal physiological metabolism in plants, thereby seriously affecting plant development. Meanwhile, plants also actively adjust their metabolism and development to adapt to changing environments. Several cold tolerance regulators have been found to participate in the regulation of plant development. Previously, we reported that BYPASS1-LIKE (B1L), a DUF793 family protein, participates in the regulation of cold tolerance, at least partly through stabilizing C-REPEAT BINDING FACTORS (CBFs). In this study, we found that B1L interacts with TRANSTHYRETIN-LIKE (TTL) protein, which is involved in brassinosteroid (BR)-mediated plant growth and catalyses the synthesis of S-allantoin, and both proteins participate in modulating plant growth and cold tolerance. The results obtained with yeast two hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that B1L directly interacted with TTL. Similar to the ttl-1 and ttl-2 mutants, the b1l mutant displayed a longer hypocotyl and greater fresh weight than wild type, whereas B1L-overexpressing lines exhibited a shorter hypocotyl and reduced fresh weight. Moreover, ttl-1 displayed freezing tolerance to cold treatment compared with WT, whereas the b1l mutant and TTL-overexpressing lines were freezing-sensitive. The b1l ttl double mutant had a developmental phenotype and freezing tolerance that were highly similar to those of ttl-1 compared to b1l, indicating that TTL is important for B1L function. Although low concentrations of brassinolide (0.1 or 1 nM) displayed similarly promoted hypocotyl elongation of WT and b1l under normal temperature, it showed less effect to the hypocotyl elongation of b1l than to that of WT under cold conditions. In addition, the b1l mutant also contained less amount of allantoin than Col-0. Our results indicate that B1L and TTL co-regulate development and cold tolerance in Arabidopsis, and BR and allantoin may participate in these processes through B1L and TTL.

中文翻译：

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促甲状腺素样蛋白和BYPASS1-LIKE共同调节拟南芥的生长和耐寒性。

冷胁迫抑制了植物的正常生理代谢，从而严重影响了植物的发育。同时，植物还积极调节其新陈代谢和发育以适应不断变化的环境。已经发现几种耐寒性调节剂参与植物发育的调节。以前，我们报道了DUF793家族蛋白BYPASS1-LIKE（B1L）至少部分通过稳定C-重复结合因子（CBF）参与抗寒性的调节。在这项研究中，我们发现B1L与跨膜促性腺激素（TTL）蛋白相互作用，后者参与油菜素甾醇（BR）介导的植物生长并催化S-丙氨酸的合成，并且这两种蛋白均参与调节植物的生长和耐寒性。酵母两个杂交（Y2H）和双分子荧光互补（BiFC）分析获得的结果表明B1L与TTL直接相互作用。与ttl-1和ttl-2突变体相似，b11l突变体显示出比野生型更长的下胚轴和更大的鲜重，而过表达B1L的品系显示出更短的下胚轴和降低的鲜重。而且，与野生型相比，ttl-1显示出对冷处理的冷冻耐受性，而b11突变体和TTL过表达株系对冷冻敏感。b11 ttl双突变体的发育表型和冷冻耐受性与ttl-1相比，与b11l高度相似，这表明TTL对于B1L功能很重要。虽然油菜素内酯的浓度低（0。1或1 nM）在正常温度下显示出WT和b11l的下胚轴伸长率得到类似的促进，而在寒冷条件下，对b11l的下胚轴伸长率的影响要小于对WT的下胚轴伸长的影响。此外，b11突变体还包含比Col-0更少的尿囊素。我们的结果表明，B1L和TTL共同调节拟南芥的发育和耐寒性，BR和尿囊素可能通过B1L和TTL参与这些过程。